Nested For Loop

for (int i = 1; i <= 3; i++) {
    for (int j = 1; j <= 4; j++) {
        System.out.println("i=" + i + ", j=" + j);
    }
}

Output:

i=1, j=1
i=1, j=2
i=1, j=3
i=1, j=4
i=2, j=1
i=2, j=2
i=2, j=3
i=2, j=4
i=3, j=1
i=3, j=2
i=3, j=3
i=3, j=4

For Each Loop (Enhanced For Loop)

int[] numbers = {3, 9, 5, -5};
for (int number : numbers) {
    System.out.println(number);
}

Output:

3
9
5
-5

Java Math Class

System.out.println(Math.max(5, 10)); // Outputs 10
System.out.println(Math.sqrt(16));   // Outputs 4.0
System.out.println(Math.random());   // Outputs a random double between 0.0 and 1.0

Sample Output:

10
4.0
0.3748293749237  (random number will vary)

Java Type Casting

int i = 100;
double d = i; // widening
System.out.println(d);

double x = 9.99;
int y = (int)x; // narrowing
System.out.println(y);

Output:

100.0
9

Array

int[] myNum = {10, 20, 30, 40};
System.out.println(myNum[2]); // Access element at index 2
myNum[2] = 50; // Change value at index 2
System.out.println(myNum[2]); // Print updated value
System.out.println(myNum.length); // Print array length

Output:

30
50
4

Multidimensional Arrays

int[][] matrix = {
    {1, 2, 3},
    {4, 5, 6}
};
System.out.println(matrix[1][2]); // Access element at 2nd row, 3rd col
matrix[1][2] = 9;
System.out.println(matrix[1][2]); // Print updated value

Output:

6
9

String Split

String sentence = "Hello World Java";
String[] words = sentence.split(" ");
for (String word : words) {
    System.out.println(word);
}

Output:

Hello
World
Java

String Contains

String s = "Hello World";
System.out.println(s.contains("World")); // true
System.out.println(s.contains("Java"));  // false

Output:

true
false

String indexOf Function

String s = "Java Programming";
int idx = s.indexOf("gram"); 
System.out.println(idx);

Output:

7

StringBuffer and StringBuilder

StringBuffer sb1 = new StringBuffer("Hello");
sb1.append(" World");
System.out.println(sb1);

// StringBuilder example
StringBuilder sb2 = new StringBuilder("Java");
sb2.insert(4, " Language");
System.out.println(sb2);

Output:

Hello World
Java Language

Date

import java.util.Date;
Date date = new Date();
System.out.println(date);

Output:

Mon Aug 04 20:00:00 IST 2025  (example output, varies with time)

LocalDate

import java.time.LocalDate;
LocalDate date = LocalDate.now();
System.out.println(date);

Output:

2025-08-04

LocalDateTime

import java.time.LocalDateTime;
LocalDateTime now = LocalDateTime.now();
System.out.println(now);

Output:

2025-08-04T20:00:00.123456789  (time part varies)

Calendar

import java.util.Calendar;
Calendar cal = Calendar.getInstance();
System.out.println(cal.getTime());

Output:

Mon Aug 04 20:00:00 IST 2025  (example output, varies with time)

Functions in Java (Methods)

public class Main {
    public static int add(int a, int b) {
        return a + b;
    }
    
    public static void main(String[] args) {
        int result = add(5, 3);
        System.out.println(result);
    }
}

Output:

8