使用Java编写的菜单驱动程序，用于执行基本的字符串操作

replace() Method: It replaces a specified character in the given string.
concat() Method: It appends another string to the end of one string.
length() Method: It returns the length of the given String.
Equals() Method: It checks whether two strings are equal or not.

for (statement 1; statement 2; statement 3) {
   // code block to be executed
}

string1.concat(string2)

string1.length() 

string1.equals(string2)

string1.replace(‘OldValue’, ‘NewValue’)

import java.util.*;
public class Main{
   public static void main(String args[]){
      System.out.println("First String");
      String s1 = "Hello";
      System.out.println("Second String");
      String s2 = "World";
      mainLoop: while (true) {
         Scanner inn = new Scanner( System.in );
         System.out.println("\n***Menu***");
         System.out.println("1. Join Two Strings");
         System.out.println("2. Get length of a String");
         System.out.println("3. Compare two Strings");
         System.out.println("4. Replace a value in String");
         System.out.println("5. Terminate the program");
         System.out.println("Enter action number (1-5): ");
         int command;
         if (inn.hasNextInt()){
            command = inn.nextInt();
            inn.nextLine();
         }
         else{
            System.out.println("\nILLEGAL RESPONSE. YOU MUST ENTER A NUMBER.");
            inn.nextLine();
            continue;
         }
         switch(command) {
            case 1:
               String joinedString = s1.concat(s2);
               System.out.println("Joined String: " + joinedString);
               break;
            case 2:
               int length1 = s1.length();
               System.out.println("Length of first String: " + length1);
               int length2 = s2.length();
               System.out.println("Length of second String: " + length2);
               break;
            case 3:
               boolean result = s1.equals(s2);
            if(result == true) {
               System.out.println("Strings first and second are equal");
            }
            else{
               System.out.println("Strings first and second are not equal");
            }
            break;
            case 4:
               String newString = s2.replace('W', 'Z');
               System.out.println("After replacing the new string is: "+newString);
               break;
            case 5:
               System.out.println("Program terminated");
               break mainLoop;
            default:
               System.out.println("Wrong choice!!");

         }
      }
   }
}

First String
Second String

***Menu***
1. Join Two Strings
2. Get length of a String
3. Compare two Strings
4. Replace a value in String
5. Terminate the program
Enter action number (1-5):
2
Length of first String: 5
Length of second String: 5

***Menu***
1. Join Two Strings
2. Get length of a String
3. Compare two Strings
4. Replace a value in String
5. Terminate the program
Enter action number (1-5):
1
Joined String: HelloWorld

***Menu***
1. Join Two Strings
2. Get length of a String
3. Compare two Strings
4. Replace a value in String
5. Terminate the program
Enter action number (1-5):
4
After replacing the new string is: Zorld

***Menu***
1. Join Two Strings
2. Get length of a String
3. Compare two Strings
4. Replace a value in String
5. Terminate the program
Enter action number (1-5):
3
Strings first and second are not equal

***Menu***
1. Join Two Strings
2. Get length of a String
3. Compare two Strings
4. Replace a value in String
5. Terminate the program
Enter action number (1-5):
5
Program terminated