It provide check for the statement.
Used to check the condtion, it checks the boolean condition True or False.
Syntax
if(boolean expression True or False){
// body
} else {
// do this
}
Example:
public class IfElse {
public static void main(String [] args){
int salary = 25400;
if(salary>10000){
salary = salary + 2000;
} else {
salary = salary + 1000;
}
System.out.printh(salary);
}
}
It executes one condition from multiple statements.
Syntax:
if(condition 1){
// code to be executed if condition 1 is true
} else if (condition 2){
// code to be executed if condition 2 is true
} else if (condtition 3){
// code to be executed if condition 2 is true
} else {
// code to be executed if condition 2 is true
}
Example:-
public class MultipleIfElse {
public static void main(String [] args){
int salary = 25400;
if(salary<=10000){
salary+=1000;
} else if(salary <= 20000){
salary += 2000;
}else{
salary += 3000;
}
System.out.println(salary);
}
}
Output :- 28400
Loops are used to iterate a part of program several times.
Is it gernerally used when we know how many times loop will iterate.
Syntax :-
for(initialization; condition; increment/decrement){
// body
}
Example: print numbers from 1 to 5
public class ForLoop {
public static void main(String [] args){
for(int num = 1; num <=5; num++){
System.out.println(num);
}
}
}
Example 2 :- print numbers from 1 to n
input java.util.Scanner;
public class ForLoop {
public static void main(String[] args){
Scanner in = new Scanner(System.in);
int n = in.nextInt();
for(int num=1; num <= n; num++){
System.out.print(num + " ");
}
}
}
It is used when we don't know how many time the loop will iterate.
Syntax
while(condition){
// code to be executed
// increment/decrement
}
Example
public class Whileloop{
public static void main(String[] args){
int num = 1;
while(num <= 5){
System.out.println(num);
num++;
}
}
}
It is used when we want to execute our statement at least one time.
Syntax
do{
// code to be executed
// update statement - increment/decrement
} while(condition);
Example :
public class doWhileloop{
public static void main(String[] args){
int n=1;
do{
System.out.println(n);
n++;
} while(n<=5);
}
}
While loop
Do while loop
→ Used when number of iteration is fixed
→ Used when we want to execute the statement at least ones
→ Entry controlled loop
→ Exit controlled loop
→ no semicolen required at the end of while (condition)
→ semicolon is required at the end of while (condition)
"Take 3 interger input from keyboard. Find the largest number among them"
Approach 1
import java.util.Scanner;
public class LargestOfThree {
public static void main(String[] args){
Scanner in = new Scanner(System.in);
int a = in.nextInt();
int b = in.nextInt();
int c = in.nextInt();
int max = a;
if(b > max){
max = b;
}
if(c > max){
max = c;
}
System.out.println(max);
}
}
Approach 2
import java.util.Scanner;
public class LargestOfThree {
public static void main(String[] args){
Scanner in = new Scanner(System.in);
int a = in.nextInt();
int b = in.nextInt();
int c = in.nextInt();
int max = 0;
if(a > b){
max = a;
} else {
max =b;
}
if(c > max){
max = c;
}
System.out.println(max);
}
}
Approach 3
Using Math.max :- Math is a class present in java.lang package and max is a function present in it which takes two number as an argument and return maximum out of them.
import java.util.Scanner;
public class LargestOfThree {
public static void main(String[] args){
Scanner in = new Scanner(System.in);
int a = in.nextInt();
int b = in.nextInt();
int c = in.nextInt();
int max = Math.max(c,Math.max(a,b));
System.out.println(max);
}
}
“ Take an input character from keyboard and check weather it is Upper case alphabet or lower case alphabet”
import java.util.Scanner;
public class AlphabetCaseCheck {
public static void main(String[] args) {
Scanner in = new Scanner (System.in);
char ch = in.next().trim().charAt(0);
if (ch > 'a' && ch <= 'z'){
System.out.println("Lowercase");
}
else {
System.out.println("Uppercase");
}
}
}
Fibonacci numbers → a series of numbers in which each number
( Fibonacci number ) is the sum of the two preceding numbers.
Ex :- 0,1,1,2,3,5,8,13…
" Given three input a, b, n a is the starting number of Fibonacci series and
b is the next number after a, n is an number to find the nth Fibonacci
number"
import java.util.Scanner;
public class FibonacciNumbers{
public static void main(String[] args) {
Scanner in = new Scanner (System.in);
int n = in.nextInt();
int a = in.nextInt();
int b = in.nextInt();
int count = 2;
while(count <= n){
int temp = b;
b = b+a;
a = temp;
count++;
}
System.out.println(b);
}
}
"Input two numbers, find that hoe many times second number
digit is present in first number"
Ex :- first number = 14458
Second number = 4
Output = 2, because 4 is present 2 times in first number
import java.util.Scanner;
public class CountingOccurence {
public static void main(String[] args) {
Scanner in = new Scanner(System.in);
int count = 0;
int Fn = in.nextInt();
int Sn = in.nextInt();
while (Fn>0){
int rem = Fn % 10;
if (rem == Sn){
count++;
}
Fn = Fn/10;
}
System.out.println(count);
}
}
"A number I input from the keyboard and Show the output as
Reverse of that number "
Example :- Input :- 12345
Output :- 54321
import java.util.Scanner;
public class ReverseANumber {
public static void main(String[] args) {
Scanner in = new Scanner(System.in);
int num = in.nextInt();
int ans = 0;
while(num > 0){
int rem = num % 10;
num /= 10;
ans = ans * 10 + rem;
}
System.out.println(ans);
}
}
import java.util.Scanner;
public class Calculator {
public static void main(String[] args) {
Scanner in = new Scanner(System.in);
// Take input from user till user does not press X or x
int ans = 0;
while (true) {
// take the operator as input
System.out.print("Enter the operator: ");
char op = in.next().trim().charAt(0);
if (op == '+' || op == '-' || op == '*' || op == '/' || op == '%') {
// input two numbers
System.out.print("Enter two numbers: ");
int num1 = in.nextInt();
int num2 = in.nextInt();
if (op == '+') {
ans = num1 + num2;
}
if (op == '-') {
ans = num1 - num2;
}
if (op == '*') {
ans = num1 * num2;
}
if (op == '/') {
if (num2 != 0) {
ans = num1 / num2;
}
}
if (op == '%') {
ans = num1 % num2;
}
} else if (op == 'x' || op == 'X') {
break;
} else {
System.out.println("Invalid operation!!");
}
System.out.println(ans);
}
}
}