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Java Examples

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Java Syntax

Create a simple "Hello World" program

Syntax Explained

Java Comments

Single-line comment before a line of code Single-line comment at the end of a line of code Multi-line comment

Comments Explained

Java Variables

Create a string variable Create an integer variable Create a variable without assigning the value, and assign the value later Overwrite an existing variable value Create a final variable (unchangeable and read-only) Combine text and a variable on display Add a variable to another variable Declare many variables of the same type with a comma-separated list

Variables Explained

Java Data Types

A demonstration of different data types in Java Create a byte type Create a short type Create an int type Create a long type Create a float type Create a double type Create a boolean type Create a char type Create a String type

Data Types Explained

Java Type Casting

Widening Casting Narrowing Casting

Type Casting Explained

Java Operators

Addition operator Subtraction operator Multiplication operator Division operator Modulus operator Increment operator Decrement operator Assignment operator Comparison operator Logical operator

Operators Explained

Java Strings

Create a string Quotes inside a string Find the length of a string Using methods to convert strings to uppercase and lowercase Finding a string in a string String concatenation If you add a number and a string, the result will be a string concatenation

Strings Explained

Java Math

Math.max(x,y) - return the highest value of x and y Math.min(x,y) - return the lowest value of x and y Math.sqrt(x) - return the square root of x Math.abs(x) - return the absolute (positive) value of x Math.random() - return a random number between 0 and 1

Java Booleans

Create a boolean type Find out if an expression is true or false Use the "equal to" operator to evaluate a boolean expression

Booleans Explained

Java If...Else (Conditions)

The if statement The else statement The else if statement

If...Else Explained

Java Switch

The switch statement The switch statement with a default keyword

Switch Explained

Java Loops

While loop Do while loop For loop For-each loop Break a loop Continue a loop

Loops Explained

Java Arrays

Create and access an array Change an array element Find the length of an array Access an array Loop through an array Loop through an array with for-each Multidimensional array Loop through a multidimensional array

Arrays Explained

Java Methods

Create and call a method Call a method multiple times Method with parameters Method with multiple parameters Return value A method with if...else Method overloading Recursion Recursive function with a halting condition

Methods Explained

Java Classes and Objects

Create a class and an object of a class Create multiple objects of a class Accessing class attributes (variables) Modify attributes Override existing attribute values Multiple attributes Create a class method Method with parameters Access class methods with an object Create a class constructor Constructor with parameters

Classes and Objects Explained

Java Modifiers

Public class Default class Public attributes Private attributes Default attributes Protected attributes Final class Abstract class with abstract methods

Modifiers Explained

Java Encapsulation

Java encapsulation (getters and setters)

Encapsulation Explained

Java Packages

Import a class from the Java API Import a package from the Java API Create a package

Packages Explained

Java Inheritance

Java inheritance (extends) Java polymorphism

Inheritance Explained

Java Inner Classes

Inner class Private inner class (error when trying to access it from an outside class) Static inner class Access outer class from inner class

Inner Classes Explained

Java Abstraction & Interfaces

Java abstract classes and methods Java interface (implements) Multiple interfaces

Interfaces Explained

Java Enums

Create an enum with a group of constants An enum inside a class An enum in a switch statement Loop through an enum

Enums Explained

Java User Input

Read user input Read user input of various types

User Input Explained

Java Dates

Display current date Display current time Display current date and time Formatting date and time

Dates Explained

Java ArrayList

Create an ArrayList Access an item in an ArrayList Remove an item from an ArrayList Remove all items from an ArrayList Get the size of an ArrayList Loop through an ArrayList Loop through an ArrayList with for-each Create an ArrayList that should store numbers (integers)

ArrayList Explained

Java HashMap

Create a HashMap Access an item in a HashMap Remove an item from a HashMap Remove all items from a HashMap Get the size of a HashMap Loop through a HashMap Create a HashMap that should store String keys and Integer values

HashMap Explained

Java HashSet

Create a HashSet and add items to it Check if an item exists in a HashSet Remove an item from a HashSet Remove all items from a HashSet Get the size of a HashSet Loop through a HashSet Create a HashSet that should store Integer values

HashSet Explained

Java Iterator

Getting an iterator Looping throug a collection Removing items from a collection

Iterator Explained

Java Wrapper Classes

Create an ArrayList that should store numbers (integers) Create wrapper objects Using wrapper methods Convert wrapper objects to strings

Wrapper Classes Explained

Java Exceptions (Try...Catch)

The try...catch statement The finally statement The throw statement

Exceptions Explained

Java Regular Expressions

Search for the word "w3schools" in a sentence

Regular Expressions Explained

Java Threads

Running a thread by extending the thread class Running a thread by implementing the Runnable interface Concurrency problems Avoid concurrency problems

Threads Explained

Java Files

Create a file Write to a file Read a file Get file information Delete a file

Files Explained

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