Find Palindrome Strings in an Array Using Java

In this article, we will see how to find all palindrome strings from an array. This is a very frequently asked questions in interview.  Also there is a question to find all palindrome number from an array.  Find few more collection interview question.  

PalindromeStrings.java

package com.techbyteslearn.lab.basic;

/**
 * This program illustrates how to find palindrome strings from an array.
 */
public class PalindromeStrings {

    public static void main(String[] args) {
        String[] stringArray = {
            "eye",
            "jdg",
            "javadevelopersguide",
            "aabaa",
            "hello",
            "pip"
        };

        for (int i = 0; i < stringArray.length; i++) {
            printOnlyPalindrome(stringArray[i]);
        }
    }

    private static void printOnlyPalindrome(String str) {
        String oldString = str;
        StringBuilder builder = new StringBuilder(str);

        if (builder.reverse().toString().equals(oldString)) {
            System.out.println(oldString + " is a Palindrome String.");
        }
    }
}

Output:

eye is a Palindrome String.
aabaa is a Palindrome String.
pip is a Palindrome String.

Happy Learning.

Reverse a String in Java Using Java API

Reverse a string using java existing API is really very easy. Below example will show you how to reverse the string using StringBuilder class.

package com.techbyteslearn.www;

public class ReverseString {

    /**
     * @param args
     */
    public static void main(String[] args) {

        String inputString = "javadevelopersguide";

        System.out.println("Before Reverse:: " + inputString);

        // You can do this using StringBuffer also, based on your requirement.
        // If you are concerned about thread safety, use StringBuffer.
        StringBuilder builder = new StringBuilder(inputString).reverse();

        // After reverse using StringBuilder
        inputString = builder.toString();

        System.out.println("After Reverse:: " + inputString);
    }
}
​

Output :-

Before Reverse::javadevelopersguide

After Reverse:: ediugsrepolevedavaj