Java

Java Example Codes

Reverse a String

import java.io.FileNotFoundException; import java.io.IOException; public class StringReverseCode { public static void main(String args[]) throws FileNotFoundException, IOException { //original string String str = "This is some string which need to be reversed"; System.out.println("Original String: " + str); //reversed string using Stringbuffer String reverseStr = new StringBuffer(str).reverse().toString(); System.out.println("Reverse String in Java using StringBuffer: " + reverseStr); //reverse String iteratively reverseStr = reverse(str); System.out.println("Reverse String in Java using Iteration: " + reverseStr); //reverse String recursively reverseStr = reverseRecursively(str); System.out.println("Reverse String in Java using Recursion: " + reverseStr); } public static String reverse(String str) { StringBuilder strBuilder = new StringBuilder(); char[] strChars = str.toCharArray(); for (int i = strChars.length - 1; i >= 0; i--) { strBuilder.append(strChars[i]); } return strBuilder.toString(); } }

Duplicate Chracters in a String

import java.util.HashMap; import java.util.Map; import java.util.Scanner; import java.util.Set; /* * This program finds duplicate charcters in a string and print them */ public class DuplicateCharacters{ public static void main(String args[]) { printDuplicateCharacters("java"); printDuplicateCharacters("cplusplus"); printDuplicateCharacters("programme"); } public static void printDuplicateCharacters(String word) { char[] characters = word.toCharArray(); // build HashMap with character and number of times they appear in String Map charMap = new HashMap(); for (Character ch : characters) { if (charMap.containsKey(ch)) { charMap.put(ch, charMap.get(ch) + 1); } else { charMap.put(ch, 1); } } // Iterate through HashMap to print all duplicate characters of String Set> entrySet = charMap.entrySet(); System.out.printf("List of duplicate characters in String '%s' %n", word); for (Map.Entry entry : entrySet) { if (entry.getValue() > 1) { System.out.printf("%s : %d %n", entry.getKey(), entry.getValue()); } } } }

Length of a String

/* * This program find the length of a given string */ public class StringFromatExample { public static void main(String[] args) { String s = "this is given string"; int strLength = s.length(); System.out.println("The length of the given string is : "+strLength); System.out.println("The length of the given string : ".length()); } }