Java Code Examples

This site lists a comprehensive collection of Java code examples categorized according to various programming concepts.

The programming concepts covered in the code examples include basic concepts, control structures, methods, arrays, classes, objects, inheritance, polymorphism, threads, file operations, data structures, sorting algorithms, mathematical functions, mathematical sequences, hashset, hashmap, exception handling, and system functions. The article provides a brief overview of the Java basics, control structures, methods, arrays, classes, objects, inheritance, polymorphism, file operations, data structures, sorting algorithms, and error handling.

In addition, it provides Java code examples with explanations and syntax for various functions such as generating random numbers, arithmetic operators, conversion programs, input/output, multidimensional arrays, dynamic and static polymorphism, and file operations like reading and writing files.

It also includes code examples for common exceptions such as ArithmeticException, ClassCastException, IndexOutOfBoundsException, and NullPointerException, and how to handle them using try-catch and throws.

Java Basics

Arithmetic operators

Bitoperators

Comments in Java

Conversion Programs

Data types in Java

Datatype String

Declaration and initialization

Escape sequences – special characters

Generate random numbers using Math.random

Generate random numbers using Random class

Generate random numbers using ThreadLocalRandom class

Hello world

Input / output

Java Code Example: check password strength

Java Code Example: convert celsius to fahrenheit

Java Code Example: convert decimal to binary number

Java Code Example: convert decimal to hexadecimal number

Java Code Example: convert decimal to octal number

Java Code Example: convert specific datatype to int

Operators in Java

Control Structures in Java

If-else syntax

Java Code Example: advanced switch-case statement

Java Code Example: check if a number is positive or negative

Java Code Example: check leap year in if else statement

Java Code Example: christmas tree pattern

Java Code Example: double nested for-loop

Java Code Example: floyd’s triangle

Java Code Example: for loop to store even and odd items in lists

Java Code Example: hourglass pattern

Java Code Example: if else statement on boolean expressions

Java Code Example: left arrow pattern

Java Code Example: multi-branches

Java Code Example: nested for loop

Java Code Example: nested if-else statement

Java Code Example: pattern reverse

Java Code Example: right arrow pattern

Java Code Example: simple calculator

Java Code Example: simple if-else statement

Java Code Example: simple pattern

Java Code Example: triangle pattern

Methods in Java

Call methods

Definition and declaration

Java Code Example: calculate cross sum (iterative and recursive)

Java Code Example: greatest common divisor (recursion)

Java Code Example: least common multiple

Java Code Example: passing array to method

Java Code Example: simple login

Java Code Example: tower of hanoi (recursive)

Java Code Example: volume and surface area of a ball

Java Code Example: volume and surface of a cube

Method overloading

Method parameters

Passing objects to methods

Recursion

Arrays in Java

Array syntax

Arrays.equals() – check two arrays for equality

Arrays.hashCode() – hash code of an array

binarySearch() – search array

Example 1: multidimensional array

Example 2: multidimensional array

fill() – fill array

Java Code Example: array in reverse order

Java Code Example: average of an array

Java Code Example: convert array to LinkedList

Java Code Example: Edit/compare multiple arrays

Java Code Example: even numbers in an array

Java Code Example: find pairs with target sum

Java Code Example: join two arrays

Java Code Example: largest number in an array

Java Code Example: odd numbers in an array

Java Code Example: prints out indices of all pairs of numbers

Java Code Example: searchs an array for a number

Java Code Example: smallest number in an array

Java Code Example: sum up all numbers from an array

Classes and Objects in Java

Array of objects

Classes and objects basics

Destructor

Encapsulation via get and set methods

Java Code Example: area of a rectangle

Java Code Example: create a small user management with customers and employees

Java Code Example: create items with counter

Java Code Example: data abstraction – public, private, protected

Java Code Example: volume of a cube

Static attributes and methods

The final keyword

Inheritance and Polymorphism in Java

Code Example 1: dynamic polymorphism

Code Example 1: static polymorphism

Code Example 2: dynamic polymorphism

Code Example 2: static polymorphism

Dynamic polymorphism

Hierarchical inheritance

Inheritance basics

Java Code Example: single inheritance

Java Code Example: static polymorphism (method overloading)

Multilevel inheritance

Single inheritance

Static polymorphism

The super keyword

Try-catch

Lambdas in Java

Basic lambda expression

Java Code Example: consumer

Java Code Example: function

Java Code Example: predicate

Lambda Expression Use Cases

Lambda Expressions in Java: filtering even numbers

Lambda Expressions in Java: iteration, filtering, and transformation

Lambda Expressions in Java: summing numbers and finding max

Lambda Expressions in Java: transforming names to uppercase

Mathematical Functions in Java

Arithmetic sequence

Basic mathematical functions

Exponential and logarithmic math functions

Fibonacci sequence

Geometric number sequence

Incremental sequence

Mathematical rounding

Prime number sequence

Square number sequence

Triangular number sequence

Trigonometric math functions

Threads in Java

Creating threads

Java Code Example: create threads from different classes

Java Code Example: create threads via for-loop

Java Code Example: two threads communicate via shared variable

Java Code Example: waiting for thread to terminate (join)

Running threads

Thread default methods

Set / Map in Java

HashMap basics

HashSet basics

Java Code Example: advanced HashMap example

Java Code Example: advanced HashSet example

Java Code Example: advanced TreeMap example

Java Code Example: advanced TreeSet example

Java Code Example: combine HashSets

Java Code Example: convert HashSet to Array

Java Code Example: HashMap alphabet

Java Code Example: simple HashMap example

Java Code Example: simple HashSet Example

Java Code Example: simple TreeMap example

Java Code Example: simple TreeSet example

TreeMap basics

TreeSet basics

System Functions in Java

Access to properties and environment variables

Copy array via system class

Create new directory

Get system date

Show all system properties

Shutdown / restart computer

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