String指的是一系列的字符。在Java中，String是对象。为了创建和操作字符串，Java提供了String类。String类有许多内置方法，用于不同的目的。
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.
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在本文中，我们将学习一些基本的字符串操作，如连接两个字符串、计算字符串长度、使用Java编程语言比较两个字符串。我们将使用switch case来实现应用程序。
展示一些实例给你看−
Instance-1
的中文翻译为：
实例-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
翻译成中文为：
实例-4
假设字符串为‘Java’，将字母‘J’替换为‘R’，那么新的字符串将是Rava。在这里将使用replace()方法。
语法
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 replace() methods respectively. 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 another new value.
以下是“for循环”的语法 -
for (statement 1; statement 2; statement 3) {
// code block to be executed
}
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Following is the syntax for concat function
string1.concat(string2)
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以下是length函数的语法
string1.length()
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Following is the syntax for equals function
string1.equals(string2)
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以下是replace函数的语法
string1.replace(‘OldValue’, ‘NewValue’)
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算法
Step-1 − Declare a String variable and initialize the value.
第二步 - 显示菜单。
Step-3 − Ask the user to enter their choice.
Step-4 − Use a switch case to go to the choice and perform the operation.
步骤-5 − 打印结果。
让我们看一下程序，以便更清楚地理解它。
Example
的中文翻译为：
示例
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!!");
}
}
}
}
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输出
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
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在本文中，我们通过使用菜单驱动的方法，探讨了如何在Java中执行简单的字符串操作。
以上就是使用Java编写的菜单驱动程序，用于执行基本的字符串操作的详细内容，更多请关注每日运维网(www.mryunwei.com)其它相关文章！
