mirror of
https://github.com/adambard/learnxinyminutes-docs.git
synced 2024-12-23 09:41:36 +00:00
Added file name param and more. See description.
-Fixed some minor issues/details -Can actually compile now (not just a bunch of random snippets) -Added more text & explanation to a few parts
This commit is contained in:
Jake Prather
parent
35a27a3337
commit
fbe0fb4718
@ -6,6 +6,8 @@ author: Jake Prather
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author_url: http://github.com/JakeHP
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filename: learnjava.java
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---
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Java is a general-purpose, concurrent, class-based, object-oriented computer programming language.
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@ -19,120 +21,120 @@ Multi-line comments look like this.
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// Import Packages
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import java.util.ArrayList;
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import package.path.here;
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// Import all "sub-packages"
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import java.lang.Math.*;
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// Your program's entry point is a function called main
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public class Main
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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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public static void main (String[] args) throws java.lang.Exception
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//main method
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public static void main (String[] args)
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{
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//stuff here
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}
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}
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// Printing, and forcing a new line on next print = 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 = 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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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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///////////////////////////////////////
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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 foo = 100;
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byte fooByte = 100;
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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 bar = 10000;
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short fooShort = 10000;
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//Integer - 32-bit signed two's complement integer
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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 foo = 1;
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int fooInt = 1;
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//Long - 64-bit signed two's complement integer
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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 bar = 100000L;
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long fooLong = 100000L;
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// (Java has no unsigned types)
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//Float - Single-precision 32-bit IEEE 754 Floating Point
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float foo = 234.5f;
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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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//Double - Double-precision 64-bit IEEE 754 Floating Point
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double bar = 123.4;
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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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//Boolean - True & False
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boolean foo = true;
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boolean bar = false;
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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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//Char - A single 16-bit Unicode character
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char foo = 'A';
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// Char - A single 16-bit Unicode character
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char fooChar = 'A';
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//Make a variable a constant
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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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//Strings
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String foo = "Hello World!";
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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 foo = "Hello World!\nLine2!";
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System.out.println(foo);
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//Hello World!
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//Line2!
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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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//Arrays
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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 [] array = new int[10];
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String [] array = new String[1];
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boolean [] array = new boolean[100];
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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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// Indexing an array - Accessing an element
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array[0];
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System.out.println("intArray @ 0: "+intArray[0]);
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// Arrays are mutable; it's just memory!
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array[1] = 1;
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System.out.println(array[1]); // => 1
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array[1] = 2;
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System.out.println(array[1]); // => 2
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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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//Others to check out
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//ArrayLists - Like arrays except more functionality is offered,
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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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// LinkedLists
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// Maps
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// HashMaps
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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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int i1 = 1, i2 = 2; // Shorthand for multiple declarations
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// Arithmetic is straightforward
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i1 + i2; // => 3
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i2 - i1; // => 1
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i2 * i1; // => 2
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i1 / i2; // => 0 (0.5, but truncated towards 0)
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System.out.println("1+2 = "+(i1 + i2)); // => 3
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System.out.println("1+2 = "+(i2 - i1)); // => 1
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System.out.println("1+2 = "+(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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11 % 3; // => 2
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System.out.println("11%3 = "+(11 % 3)); // => 2
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// Comparison operators
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3 == 2; // => 0 (false)
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3 != 2; // => 1 (true)
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3 > 2; // => 1
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3 < 2; // => 0
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2 <= 2; // => 1
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2 >= 2; // => 1
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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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@ -140,100 +142,110 @@ i1 / i2; // => 0 (0.5, but truncated towards 0)
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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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i++; //i = 1. Post-Incrementation
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++i; //i = 2. Pre-Incrementation
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i--; //i = 1. Post-Decrementation
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--i; //i = 0. Pre-Decrementation
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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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if (false) {
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System.out.println("I never run");
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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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System.out.println("I print");
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}
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System.out.println("\n->Control Structures");
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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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System.out.println("I am also never run");
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} else {
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System.out.println("I print");
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}
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// While loop
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int i = 0;
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while(i < 100){
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System.out.println(i);
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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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i++;
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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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// Do While Loop
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int i = 0;
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do{
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System.out.println(i);
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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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i++;
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}while(i < 100);
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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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// For Loop
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int i;
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int fooFor;
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//for loop structure => for(<start_statement>;<conditional>;<step>)
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for(i=0;i<100;i++){
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System.out.println(i);
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for(fooFor=0;fooFor<100;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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// 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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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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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(monthString);
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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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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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// Typecasting
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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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// 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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// 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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// 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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// Typecsating
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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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@ -243,66 +255,77 @@ Integer.toString(123);//returns a string version of 123
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// Classes And Functions
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///////////////////////////////////////
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// Classes Syntax shown below.
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// Function declaration 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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// 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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Bicycle trek = new Bicycle();
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// Manipulate your object
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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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public 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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// 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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gear = 1;
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cadence = 50;
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startGear = 1;
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}
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// This is a specified constructor (it contains arguments)
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public Bicycle(int startCadence, int startSpeed, int startGear) {
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gear = startGear;
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cadence = startCadence;
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speed = startSpeed;
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}
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// the Bicycle class has
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// four methods
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public void setCadence(int newValue) {
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cadence = newValue;
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}
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public void setGear(int newValue) {
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gear = newValue;
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}
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public void applyBrake(int decrement) {
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speed -= decrement;
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}
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public void speedUp(int increment) {
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speed += increment;
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}
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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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//Now..Later in the main / driver of your java program
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public class Main
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{
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public static void main (String[] args) throws java.lang.Exception
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{
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//Call bicycle's constructor
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Bicycle trek = new Bicycle();
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//Manipulate your object
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trek.speedUp(3);
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trek.setCadence(100);
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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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// 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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gear = 1;
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cadence = 50;
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speed = 5;
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}
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// This is a specified constructor (it contains arguments)
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public Bicycle(int startCadence, int startSpeed, int startGear) {
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gear = startGear;
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cadence = startCadence;
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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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public void setCadence(int newValue) {
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cadence = newValue;
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}
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public void setGear(int newValue) {
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gear = newValue;
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}
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public void applyBrake(int decrement) {
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speed -= decrement;
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}
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public void speedUp(int increment) {
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speed += increment;
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}
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public String toString(){
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return "gear: "+Integer.toString(gear)+
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" cadence: "+Integer.toString(cadence)+
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" speed: "+Integer.toString(speed);
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}
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// bracket to close nested Bicycle class
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}
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// bracket to close learnjava.java
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}
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```
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