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Updated java
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Adam
parent
87670d3bb6
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b58a7d9d23
@ -24,273 +24,261 @@ import java.util.ArrayList;
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// Import all classes inside of java.lang package
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import java.security.*;
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// Inside of the LearnJava class, is your program's
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// starting point. The main method.
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public class LearnJava
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{
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//main method
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public static void main (String[] args)
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{
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// Each .java file contains one public class, with the same name as the file.
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public class LearnJava {
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System.out.println("->Printing");
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// Printing, and forcing a new line on next print, use println()
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System.out.println("Hello World!");
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System.out.println("Integer: "+10+" Double: "+3.14+ " Boolean: "+true);
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// Printing, without forcing a new line on next print, use print()
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System.out.print("Hello World - ");
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System.out.print("Integer: "+10+" Double: "+3.14+ " Boolean: "+true);
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// A program must have a main method as an entry point
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public static void main (String[] args) {
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///////////////////////////////////////
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// Types
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///////////////////////////////////////
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System.out.println("\n\n->Types");
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// Byte - 8-bit signed two's complement integer
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// (-128 <= byte <= 127)
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byte fooByte = 100;
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// Use System.out.println to print lines
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System.out.println("Hello World!");
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System.out.println("Integer: " + 10 + " Double: " + 3.14 + " Boolean: " + true);
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// Short - 16-bit signed two's complement integer
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// (-32,768 <= short <= 32,767)
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short fooShort = 10000;
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// To print without a newline, use System.out.print
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System.out.print("Hello ");
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System.out.print("World");
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// Integer - 32-bit signed two's complement integer
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// (-2,147,483,648 <= int <= 2,147,483,647)
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int fooInt = 1;
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// Long - 64-bit signed two's complement integer
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// (-9,223,372,036,854,775,808 <= long <= 9,223,372,036,854,775,807)
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long fooLong = 100000L;
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///////////////////////////////////////
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// Types & Variables
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///////////////////////////////////////
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// (Java has no unsigned types)
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// Declare a variable using <type> <name> [
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// Byte - 8-bit signed two's complement integer
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// (-128 <= byte <= 127)
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byte fooByte = 100;
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// Float - Single-precision 32-bit IEEE 754 Floating Point
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float fooFloat = 234.5f;
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// Short - 16-bit signed two's complement integer
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// (-32,768 <= short <= 32,767)
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short fooShort = 10000;
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// Double - Double-precision 64-bit IEEE 754 Floating Point
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double fooDouble = 123.4;
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// Integer - 32-bit signed two's complement integer
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// (-2,147,483,648 <= int <= 2,147,483,647)
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int fooInt = 1;
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// Boolean - True & False
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boolean fooBoolean = true;
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boolean barBoolean = false;
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// Long - 64-bit signed two's complement integer
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// (-9,223,372,036,854,775,808 <= long <= 9,223,372,036,854,775,807)
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long fooLong = 100000L;
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// Char - A single 16-bit Unicode character
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char fooChar = 'A';
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// (Java has no unsigned types)
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// Make a variable a constant
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final int HOURS_I_WORK_PER_WEEK = 9001;
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// Float - Single-precision 32-bit IEEE 754 Floating Point
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float fooFloat = 234.5f;
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// Strings
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String fooString = "My String Is Here!";
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// \n is an escaped character that starts a new line
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String barString = "Printing on a new line?\nNo Problem!";
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System.out.println(fooString);
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System.out.println(barString);
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// Double - Double-precision 64-bit IEEE 754 Floating Point
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double fooDouble = 123.4;
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// Arrays
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//The array size must be decided upon declaration
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//The format for declaring an array is follows:
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//<datatype> [] <var name> = new <datatype>[<array size>];
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int [] intArray = new int[10];
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String [] stringArray = new String[1];
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boolean [] booleanArray = new boolean[100];
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// Boolean - true & false
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boolean fooBoolean = true;
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boolean barBoolean = false;
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// Another way to declare & initialize an array
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int [] y = {9000, 1000, 1337};
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// Char - A single 16-bit Unicode character
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char fooChar = 'A';
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// Indexing an array - Accessing an element
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System.out.println("intArray @ 0: "+intArray[0]);
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// Use final to make a variable immutable
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final int HOURS_I_WORK_PER_WEEK = 9001;
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// Arrays are mutable; it's just memory!
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intArray[1] = 1;
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System.out.println("intArray @ 1: "+intArray[1]); // => 1
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intArray[1] = 2;
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System.out.println("intArray @ 1: "+intArray[1]); // => 2
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// Strings
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String fooString = "My String Is Here!";
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// Others to check out
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// ArrayLists - Like arrays except more functionality is offered,
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// and the size is mutable
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// LinkedLists
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// Maps
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// HashMaps
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// \n is an escaped character that starts a new line
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String barString = "Printing on a new line?\nNo Problem!";
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System.out.println(fooString);
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System.out.println(barString);
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///////////////////////////////////////
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// Operators
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///////////////////////////////////////
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System.out.println("\n->Operators");
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// Arrays
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//The array size must be decided upon declaration
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//The format for declaring an array is follows:
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//<datatype> [] <var name> = new <datatype>[<array size>];
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int [] intArray = new int[10];
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String [] stringArray = new String[1];
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boolean [] booleanArray = new boolean[100];
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int i1 = 1, i2 = 2; // Shorthand for multiple declarations
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// Another way to declare & initialize an array
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int [] y = {9000, 1000, 1337};
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// Arithmetic is straightforward
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System.out.println("1+2 = "+(i1 + i2)); // => 3
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System.out.println("2-1 = "+(i2 - i1)); // => 1
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System.out.println("2*1 = "+(i2 * i1)); // => 2
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System.out.println("1/2 = "+(i1 / i2)); // => 0 (0.5, but truncated towards 0)
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// Indexing an array - Accessing an element
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System.out.println("intArray @ 0: " + intArray[0]);
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// Modulo
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System.out.println("11%3 = "+(11 % 3)); // => 2
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// Arrays are zero-indexed and mutable.
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intArray[1] = 1;
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System.out.println("intArray @ 1: " + intArray[1]); // => 1
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// Comparison operators
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System.out.println("3 == 2? "+(3 == 2)); // => 0 (false)
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System.out.println("3 != 2? "+(3 != 2)); // => 1 (true)
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System.out.println("3 > 2? "+(3 > 2)); // => 1
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System.out.println("3 < 2? "+(3 < 2)); // => 0
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System.out.println("2 <= 2? "+(2 <= 2)); // => 1
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System.out.println("2 >= 2? "+(2 >= 2)); // => 1
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// Others to check out
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// ArrayLists - Like arrays except more functionality is offered,
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// and the size is mutable
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// LinkedLists
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// Maps
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// HashMaps
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// Bitwise operators!
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/*
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~ Unary bitwise complement
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<< Signed left shift
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>> Signed right shift
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>>> Unsigned right shift
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& Bitwise AND
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^ Bitwise exclusive OR
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| Bitwise inclusive OR
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*/
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///////////////////////////////////////
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// Operators
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///////////////////////////////////////
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System.out.println("\n->Operators");
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// Incrementations
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int i=0;
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System.out.println("\n->Inc/Dec-rementation");
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System.out.println(i++); //i = 1. Post-Incrementation
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System.out.println(++i); //i = 2. Pre-Incrementation
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System.out.println(i--); //i = 1. Post-Decrementation
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System.out.println(--i); //i = 0. Pre-Decrementation
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int i1 = 1, i2 = 2; // Shorthand for multiple declarations
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///////////////////////////////////////
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// Control Structures
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///////////////////////////////////////
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System.out.println("\n->Control Structures");
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if (false){
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// Arithmetic is straightforward
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System.out.println("1+2 = " + (i1 + i2)); // => 3
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System.out.println("2-1 = " + (i2 - i1)); // => 1
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System.out.println("2*1 = " + (i2 * i1)); // => 2
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System.out.println("1/2 = " + (i1 / i2)); // => 0 (0.5, but truncated towards 0)
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// Modulo
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System.out.println("11%3 = "+(11 % 3)); // => 2
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// Comparison operators
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System.out.println("3 == 2? " + (3 == 2)); // => 0 (false)
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System.out.println("3 != 2? " + (3 != 2)); // => 1 (true)
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System.out.println("3 > 2? " + (3 > 2)); // => 1
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System.out.println("3 < 2? " + (3 < 2)); // => 0
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System.out.println("2 <= 2? " + (2 <= 2)); // => 1
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System.out.println("2 >= 2? " + (2 >= 2)); // => 1
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// Bitwise operators!
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/*
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~ Unary bitwise complement
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<< Signed left shift
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>> Signed right shift
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>>> Unsigned right shift
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& Bitwise AND
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^ Bitwise exclusive OR
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| Bitwise inclusive OR
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*/
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// Incrementations
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int i=0;
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System.out.println("\n->Inc/Dec-rementation");
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System.out.println(i++); //i = 1. Post-Incrementation
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System.out.println(++i); //i = 2. Pre-Incrementation
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System.out.println(i--); //i = 1. Post-Decrementation
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System.out.println(--i); //i = 0. Pre-Decrementation
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///////////////////////////////////////
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// Control Structures
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///////////////////////////////////////
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System.out.println("\n->Control Structures");
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// If statements are c-like
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if (false){
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System.out.println("I never run");
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}else if (false) {
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}else if (false) {
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System.out.println("I am also never run");
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} else {
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} else {
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System.out.println("I print");
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}
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}
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// While loop
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int fooWhile = 0;
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while(fooWhile < 100)
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{
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// While loop
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int fooWhile = 0;
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while(fooWhile < 100)
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{
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//System.out.println(fooWhile);
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//Increment the counter
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//Iterated 99 times, fooWhile 0->99
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fooWhile++;
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}
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System.out.println("fooWhile Value: "+fooWhile);
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}
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System.out.println("fooWhile Value: " + fooWhile);
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// Do While Loop
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int fooDoWhile = 0;
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do
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{
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// Do While Loop
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int fooDoWhile = 0;
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do
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{
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//System.out.println(fooDoWhile);
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//Increment the counter
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//Iterated 99 times, fooDoWhile 0->99
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fooDoWhile++;
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}while(fooDoWhile < 100);
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System.out.println("fooDoWhile Value: "+fooDoWhile);
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}while(fooDoWhile < 100);
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System.out.println("fooDoWhile Value: " + fooDoWhile);
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// For Loop
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int fooFor;
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//for loop structure => for(<start_statement>;<conditional>;<step>)
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for(fooFor=0;fooFor<100;fooFor++){
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// For Loop
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int fooFor;
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//for loop structure => for(<start_statement>; <conditional>; <step>)
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for(fooFor=0; fooFor<10; fooFor++){
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//System.out.println(fooFor);
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//Iterated 99 times, fooFor 0->99
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}
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System.out.println("fooFor Value: "+fooFor);
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//Iterated 10 times, fooFor 0->9
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}
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System.out.println("fooFor Value: " + fooFor);
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// Switch Case
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int month = 8;
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String monthString;
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switch (month){
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// Switch Case
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int month = 3;
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String monthString;
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switch (month){
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case 1: monthString = "January";
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break;
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case 2: monthString = "February";
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break;
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case 3: monthString = "March";
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break;
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case 4: monthString = "April";
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default: monthString = "Some other month";
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break;
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case 5: monthString = "May";
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break;
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case 6: monthString = "June";
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break;
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case 7: monthString = "July";
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break;
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case 8: monthString = "August";
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break;
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case 9: monthString = "September";
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break;
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case 10: monthString = "October";
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break;
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case 11: monthString = "November";
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break;
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case 12: monthString = "December";
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break;
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default: monthString = "Invalid month";
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break;
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}
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System.out.println("Switch Case Result: "+monthString);
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///////////////////////////////////////
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// Converting Data Types And Typcasting
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///////////////////////////////////////
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// Converting data
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// Convert String To Integer
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Integer.parseInt("123");//returns an integer version of "123"
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// Convert Integer To String
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Integer.toString(123);//returns a string version of 123
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// For other conversions check out the following classes:
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// Double
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// Long
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// String
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// Typecasting
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// You can also cast java objects, there's a lot of details and
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// deals with some more intermediate concepts.
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// Feel free to check it out here: http://docs.oracle.com/javase/tutorial/java/IandI/subclasses.html
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}
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System.out.println("Switch Case Result: " + monthString);
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///////////////////////////////////////
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// Classes And Functions
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///////////////////////////////////////
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///////////////////////////////////////
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// Converting Data Types And Typcasting
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///////////////////////////////////////
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// Converting data
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// Convert String To Integer
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Integer.parseInt("123");//returns an integer version of "123"
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// Convert Integer To String
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Integer.toString(123);//returns a string version of 123
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// For other conversions check out the following classes:
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// Double
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// Long
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// String
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// Typecasting
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// You can also cast java objects, there's a lot of details and
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// deals with some more intermediate concepts.
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// Feel free to check it out here:
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// http://docs.oracle.com/javase/tutorial/java/IandI/subclasses.html
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///////////////////////////////////////
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// Classes And Functions
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///////////////////////////////////////
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// Read about the class, and function syntax before
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// reading this.
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System.out.println("\n->Classes & Functions");
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// Call bicycle's constructor
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// (definition of the Bicycle class follows)
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// Use new to instantiate a class
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Bicycle trek = new Bicycle();
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// Manipulate your object
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// Call object methods
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trek.speedUp(3);
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trek.setCadence(100);
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System.out.println("trek info: "+trek.toString());
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// Classes Syntax:
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// <public/private/protected> class <class name>{
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// //data fields, constructors, functions all inside
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// }
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// Function Syntax:
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// <public/private/protected> <return type> <function name>(<args>)
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// Here is a quick rundown on access level modifiers (public, private, etc.)
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// http://docs.oracle.com/javase/tutorial/java/javaOO/accesscontrol.html
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// toString is a convention
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System.out.println("trek info: " + trek.toString());
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// This bracket ends the main method
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}
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// The static field is only required because this class
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// is nested inside of the learnjava.java class.
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public static class Bicycle {
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} // End main method
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} // End LearnJava class
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// You can include other, non-public classes in a .java file
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// Class Declaration Syntax:
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// <public/private/protected> class <class name>{
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// //data fields, constructors, functions all inside
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// }
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class Bicycle {
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// Bicycle's Fields/Variables
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public int cadence;
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public int gear;
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public int speed;
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public int cadence; // Public: Can be accessed from anywhere
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private int speed; // Private: Only accessable from within the class
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protected int gear; // Protected: Accessible from the class and subclasses
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// Constructors are a way of creating classes
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// This is a default constructor
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public Bicycle(){
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public Bicycle() {
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gear = 1;
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cadence = 50;
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speed = 5;
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@ -303,8 +291,18 @@ Integer.toString(123);//returns a string version of 123
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speed = startSpeed;
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}
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// the Bicycle class has
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// four functions/methods
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// Function Syntax:
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// <public/private/protected> <return type> <function name>(<args>)
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// Java classes often implement getters and setters for their fields
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// Method declaration syntax:
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// <scope> <return type> <method name>(<args>)
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public int getCadence() {
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return cadence;
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}
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// void methods require no return statement
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public void setCadence(int newValue) {
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cadence = newValue;
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}
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@ -313,22 +311,37 @@ Integer.toString(123);//returns a string version of 123
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gear = newValue;
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}
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|
||||
public void applyBrake(int decrement) {
|
||||
speed -= decrement;
|
||||
}
|
||||
|
||||
public void speedUp(int increment) {
|
||||
speed += increment;
|
||||
}
|
||||
|
||||
public String toString(){
|
||||
public void slowDown(int decrement) {
|
||||
speed -= decrement;
|
||||
}
|
||||
|
||||
public String toString() {
|
||||
return "gear: "+Integer.toString(gear)+
|
||||
" cadence: "+Integer.toString(cadence)+
|
||||
" speed: "+Integer.toString(speed);
|
||||
}
|
||||
// bracket to close nested Bicycle class
|
||||
} // end class Bicycle
|
||||
|
||||
// Use `extends` to extend a class
|
||||
class PennyFarthing extends Bicycle {
|
||||
// (Penny Farthings are those bicycles with the big front wheel.
|
||||
// They have no gears.)
|
||||
|
||||
public PennyFarthing(int startCadence, int startSpeed){
|
||||
// Call the parent constructor with super
|
||||
super(startCadence, startSpeed, 0);
|
||||
}
|
||||
// bracket to close learnjava.java
|
||||
|
||||
// You should mark a method you're overriding with an @annotation
|
||||
@Override
|
||||
public void setGear(int gear) {
|
||||
gear = 0;
|
||||
}
|
||||
|
||||
}
|
||||
|
||||
```
|
||||
|
||||
Loading…
Reference in New Issue
Block a user