Java 如何在子字符串前后打印字符串，然后将新字符串添加到旧字符串中？

我正在尝试制作一个程序，可以读取子字符串前后的字符串，然后要求用户添加一个新字符串并打印新字符串用户喜欢的位置是一个示例：

下面是我正在执行的代码：

import java.util.Scanner;

public class Project02 {

    public static void main(String[] args) {

        Scanner name = new Scanner (System.in);

        System.out.println("Enter a long string: ");
        String username = name.nextLine();
        System.out.println("Enter a substring: ");
        String subname = name.nextLine();
        System.out.println("Length of your string: "+ username.length());
        System.out.println("Length of your substring: " + subname.length());
        System.out.println( "Starting position of your substring in string: "+ username.indexOf(subname));

        System.out.println("Enter a replacement string: ");
        String newname = name.nextLine();
        System.out.println("Your new string is: "+ );


    }

}

因此：

---

输入的子字符串前面的字符串应该是

username.substring（0，username.indexOf（subname）

，然后后面的字符串应该是

username.substring（username.indexOf（subname）+subname.length）

。然后在这两个子字符串之间打印新字符串。

当我在这两个子字符串之间添加新字符串时，用户子字符串被删除。这里是我添加的代码：“System.out.println”（“输入替换字符串：”）；string newname=name.nextLine（）；System.out.println（“您的新字符串是：”+username.substring（0，username.indexOf（子名称））+“”+newname+“”+username.substring（username.indexOf（子名称）+subname.length（））；“是的，应该这样做。虽然不需要在每个组件字符串之间添加空格。这是打印新字符串时的样子，但会删除旧字符串

import java.util.Scanner;

public class Project02 {

    public static void main(String[] args) {

        Scanner name = new Scanner (System.in);

        System.out.println("Enter a long string: ");
        String username = name.nextLine();
        System.out.println("Enter a substring: ");
        String subname = name.nextLine();
        System.out.println("Length of your string: "+ username.length());
        System.out.println("Length of your substring: " + subname.length());
        System.out.println( "Starting position of your substring in string: "+ username.indexOf(subname));

        System.out.println("Enter a replacement string: ");
        String newname = name.nextLine();
        System.out.println("Your new string is: "+ );


    }

}

int index = text.indexOf(substring);
String left = text.substring(0, index);
String right = text.substring(index + substring.length());
String replacement = name.nextLine();
String newText = left + replacement + right;