Best Java Cheat Sheet:

https://introcs.cs.princeton.edu/java/11cheatsheet/

// JAVA PROGRAMMING CHEATSHEET

​

// COMMENTS

// Single-line comment

​

/*

   Multi-line

   comment

*/

​

// DATA TYPES

// Primitive data types

byte    // 1 byte   (range: -128 to 127)

short   // 2 bytes  (range: -32,768 to 32,767)

int     // 4 bytes  (range: -2^31 to 2^31-1)

long    // 8 bytes  (range: -2^63 to 2^63-1)

float   // 4 bytes  (decimal precision: 7 digits)

double  // 8 bytes  (decimal precision: 15-16 digits)

char    // 2 bytes  (single character)

boolean // 1 bit    (true or false)

​

// VARIABLES

dataType variableName = value; // Variable declaration and initialization

​

// CONSTANTS

final dataType CONSTANT_NAME = value; // Declare a constant

​

// CONDITIONAL STATEMENTS

if (condition) {

    // Code to execute if the condition is true

} else if (anotherCondition) {

    // Code to execute if the first condition is false and this one is true

} else {

    // Code to execute if all conditions are false

}

​

// SWITCH STATEMENT

switch (variable) {

    case value1:

        // Code to execute if variable is equal to value1

        break;

    case value2:

        // Code to execute if variable is equal to value2

        break;

    default:

        // Code to execute if variable does not match any case

        break;

}

​

// LOOPS

// For loop

for (int i = 0; i < limit; i++) {

    // Code to repeat

}

​

// While loop

while (condition) {

    // Code to repeat as long as the condition is true

}

​

// Do-While loop

do {

    // Code to repeat at least once before checking the condition

} while (condition);

​

// ARRAYS

dataType[] arrayName = new dataType[size]; // Declaration and initialization of an array

​

// METHODS (FUNCTIONS)

dataType methodName(parameter1Type parameter1, parameter2Type parameter2) {

    // Method code

    return result; // Optional return statement

}

​

// OBJECTS AND CLASSES

class ClassName {

    dataType attribute1;

    dataType attribute2;

​

    ClassName(dataType param1, dataType param2) {

        // Constructor code

    }

​

    dataType methodName(parameterType param) {

        // Method code

    }

}

​

// OBJECT CREATION

ClassName objectName = new ClassName(arg1, arg2);

​

// INHERITANCE

class Subclass extends Superclass {

    // Subclass-specific attributes and methods

}

​

// INTERFACE

interface InterfaceName {

    // Method signatures (methods without implementation)

}

​

// IMPLEMENT INTERFACE

class ClassName implements InterfaceName {

    // Implement the interface's methods

}

​

// EXCEPTION HANDLING

try {

    // Code that might throw an exception

} catch (ExceptionType exceptionName) {

    // Code to handle the exception

} finally {

    // Code that always executes, regardless of exception

}

​

// FILE I/O

import java.io.*; // Import the required package

​

// Read from a file

BufferedReader reader = new BufferedReader(new FileReader("filename.txt"));

String line;

while ((line = reader.readLine()) != null) {

    // Process the line

}

reader.close();

​

// Write to a file

BufferedWriter writer = new BufferedWriter(new FileWriter("filename.txt"));

writer.write("Hello, World!");

writer.close();