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Reverse An Integer In Java
Reverse an Integer in Java is a part of our Java code examples series. This is a very common question for junior level java developers.
Interview Problem Statement
- Reverse an integer in Java without using any API.
- Reverse a number in Java.
20 Java Regular Expressions Quiz Regex Questions [MCQ]
Code Example
package com.adevguide.java.problems;
public class ReverseInteger {
public static void main(String[] args) {
// Variable to hold input value
Integer input = 123;
// Variable to hold reversed value
Integer reverse = 0;
// loop till input value becomes zero
while (input != 0) {
// multiple previous reverse value by 10 , add the remainder to it and save it back
// in reverse variable
reverse = reverse * 10 + input % 10;
// Divide input by 10 and store quotient value in input
input = input / 10;
}
// Print reverse Value
System.out.println("Reverse Integer ::" + reverse);
}
}
Code Explanation
To reverse an integer in Java, we will follow the following steps:
- Find one’s place of the input and add it to 10 x previously calculated reverse value.
- Change input value to the quotient of division of input by 10.
Example:
Input = 123
Iteration 1:
reverse = 0 * 10 + 123 % 10
reverse = 3
Input = 12
Iteration 2:
reverse = 3 * 10 + 12 % 10
reverse = 32
Input = 1
Iteration 3:
reverse = 32 * 10 + 1 % 10
reverse = 321
Input = 0
Source Code
As always, you can find all our source code at GitHub.
