Java CheatSheet | Beginners, Intermediate | Part-1

Basics

Basic syntax and functions from the Java programming language.

Boilerplate

class HelloWorld{ 
public static void main(String args[]){ 
System.out.println("Hello World"); 
} 
}

Showing Output

It will print something to the output console.

System.out.println([text])

Taking Input

It will take string input from the user

import java.util.Scanner; //import scanner class

// create an object of Scanner class
Scanner input = new Scanner(System.in);

// take input from the user
String varName = input.nextLine();

Primitive Type Variables

The eight primitives defined in Java are int, byte, short, long, float, double, boolean, and char those aren't considered objects and represent raw values.

byte

byte is a primitive data type it only takes up 8 bits of memory.

age = 18;

long

long is another primitive data type related to integers. long takes up 64 bits of memory.

viewsCount = 3_123_456L;

float

We represent basic fractional numbers in Java using the float type. This is a single-precision decimal number. Which means if we get past six decimal points, this number becomes less precise and more of an estimate.

price = 100INR;

char

Char is a 16-bit integer representing a Unicode-encoded character.

letter = 'A';

boolean

The simplest primitive data type is boolean. It can contain only two values: true or false. It stores its value in a single bit.

isEligible = true;

int

int holds a wide range of non-fractional number values.

var1 = 256;

short

If we want to save memory and byte is too small, we can use short.

short var2 = 786;

Comments

A comment is the code that is not executed by the compiler, and the programmer uses it to keep track of the code.

Single line comment

// It's a single line comment

Multi-line comment

/* It's a 
multi-line
comment
*/

Constants

Constants are like a variable, except that their value never changes during program execution.

final float INTEREST_RATE = 0.04;

Arithmetic Expressions

These are the collection of literals and arithmetic operators.

Addition

It can be used to add two numbers

int x = 10 + 3;