使用Java編寫的選單驅動程序，用於執行基本的字串操作

String指的是一系列的字元。在Java中，String是物件。為了創建和操作字串，Java提供了String類別。 String類別有許多內建方法，用於不同的目的。

We will perform a few basic string operations by using inbuilt String methods.

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.

在本文中，我們將學習一些基本的字串操作，例如連接兩個字串、計算字串長度、使用Java程式語言比較兩個字串。我們將使用switch case來實作應用程式。

展示一些實例給你看−

Instance-1

的中文翻譯為：

實例-1

Suppose the first String is ‘Java’ and the second String is ‘Python’ then by joining two String will give ‘JavaPython’. Here the concat() method will be used.

Instance-2

Suppose the first String is ‘Java’ and the second String is ‘Python’ then by counting two String will give its respective length as 4 and 6. Here length() method will be used.

Instance-3

Suppose the first String is ‘Java’ and the second String is ‘Python’ then by comparing two String will give “Both strings are not equal”. Here equals() method will be used.

##」 Instance-4翻譯成中文為：

實例-4

假設字串為‘Java’，將字母‘J’替換為‘R’，那麼新的字串將是Rava。這裡將使用replace()方法。

文法

To perform basic string operations like joining the string, getting length of the string, comparing the string and replacing a specific value in a String we use concat(), length(), equals() and respecals() and respective) . The concat() method

appends (concatenate) a string to the end of another string

. The length() method

returns the length of a specified string

. The length of an empty string is 0. The equals() method

compares two strings, and returns true if the strings are equal, and false if not

. The replace() method

replaces a specified value in a String with an new valuean new value .

以下是「for迴圈」的語法 -###

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

###Following is the syntax for concat function###

string1.concat(string2)

###以下是length函數的語法###

string1.length() 

###Following is the syntax for equals function###

string1.equals(string2)

###以下是replace函數的語法###

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

###演算法### ######Step-1### − Declare a String variable and initialize the value.### ######第二步### - 顯示選單。 ### ######Step-3### − Ask the user to enter their choice.### ######Step-4### − Use a switch case to go to the choice and perform the operation.### ######步驟-5### − 列印結果。 ### ###讓我們看一下程序，以便更清楚地理解它。 ### ###Example###的中文翻譯為：###範例###

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!!");

         }
      }
   }
}

###輸出###

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

######在本文中，我們透過使用選單驅動的方法，探討如何在Java中執行簡單的字串操作。 ######

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