Question

我必须在我的代码中使用循环，以便当有人输入yes时，他们可以根据需要重复输入他们的名字，但我不知道如何执行此操作。任何帮助表示赞赏，这是我的代码：

public static void main(String [] args)
  {
    // Create a Scanner object to read input.
    Scanner keyboard = new Scanner(System.in);

    //Get the user's name.
    System.out.print("What is your name?");
    String name = keyboard.nextLine();
    System.out.println("Hello there," + name);

    System.out.println("Would you like to enter another name? Please enter Yes Or No.");
    String reply = keyboard.nextLine();

    if (reply == "yes")
    {

    }
  }
}

Answer 1

这个reply == "yes"不是你在Java中比较String的方式。这比较了内存位置，而不是内容（并且内存位置不太可能相等）。

相反，您需要使用reply.equals("yes")，或者如果您不关心进行案例比较，则可以使用reply.equalsIgnoreCase("yes")代替

do {
    // The remainder of your code...
} while (reply.equalsIgnoreCase("yes"));

<强>更新

您可能还希望阅读The while and do-while statements和The for Statement，其中介绍了使用Java循环的基础知识

Answer 2

使用do-while循环：

public static void main(String[] args) {

        // Create a Scanner object to read input.
        Scanner keyboard = new Scanner(System.in);
        do {
            //Get the user's name.
            System.out.print("What is your name?");
            String name = keyboard.nextLine();
            System.out.println("Hello there," + name);
            System.out.println("Would you like to enter another name? Please enter Yes Or No.");

        } while (keyboard.nextLine().equalsIgnoreCase("yes"));

        System.out.println("Bye!");
        keyboard.close();
      }
    }

Answer 3

我认为这可行（未经测试）：

public static Scanner keyboard = new Scanner(System.in); // global

    public static void main(String [] args)
    {
        getName();
    }

    public static void getName()
    {
        System.out.print("What is your name?");
        String name = keyboard.nextLine();
        System.out.println("Hello there," + name);
        rerun();
    }

    public static void rerun()
    {
        System.out.println("Would you like to enter another name? Please enter \"yes\" or \"no\".");
        String reply = keyboard.nextLine();

        if (reply.equals("yes")) getName();
        else System.exit();
    }

}

首先我们调用getName()方法并运行一次。然后我们调用rerun()方法。此方法将测试是否要重新运行该程序。如果用户输入“是”，那么我们重复整个过程。如果我们输入除“是”之外的任何内容，程序将退出。

除了您的代码未完成之外，您的代码唯一真正的问题是您尝试将字符串与==运算符进行比较。请参阅MadProgrammer的答案，了解为什么这是错误的。

Answer 4

使用此

import java.util.*;
public class prob13 {
public static void main(String [] args)
  {
    // Create a Scanner object to read input.
    Scanner keyboard = new Scanner(System.in);

    //Get the user's name.
    while(true){
        System.out.print("What is your name?");
        String name = keyboard.nextLine();
        System.out.println("Hello there," + name);

        System.out.println("Would you like to enter another name? Please enter Yes Or No.");
        String reply = keyboard.nextLine();

        if(reply.equals("no"))
            break;
    }
 }
}

只要答案不是否，原因就是循环。

如果您希望答案始终为是

，则可以使用此功能

import java.util.*;
public class prob13 {
public static void main(String [] args)
  {
    // Create a Scanner object to read input.
    Scanner keyboard = new Scanner(System.in);
        String reply="yes";
    //Get the user's name.
    while(reply.equals("yes")){
        System.out.print("What is your name?");
        String name = keyboard.nextLine();
        System.out.println("Hello there," + name);

        System.out.println("Would you like to enter another name? Please enter Yes Or No.");
        reply = keyboard.nextLine();

    }
 }
}

Answer 5

最简单（也可能是最清晰）的方法是在do-while statement中包装您想要重复的内容：

public static void main(String [] args)
  {
    // Create a Scanner object to read input.
    Scanner keyboard = new Scanner(System.in);

    String reply;
    do {
        //Get the user's name.
        System.out.print("What is your name?");
        String name = keyboard.nextLine();
        System.out.println("Hello there," + name);

        System.out.println("Would you like to enter another name? Please enter Yes Or No.");
        reply = keyboard.nextLine();

    } while ("yes".equals(reply));
  }
}

必须在块之前声明reply变量，因为它是在循环条件下访问的（变量只在声明的块中可见，因此如果在循环中声明了回复，则它不可用于循环条件）。

我改变了循环条件，因为==运算符通过引用比较字符串，即它将检查双方是否指向同一个String对象。相反，equals方法检查字符串的内容是否相等（即它们包含相同顺序的相同字符）。

Answer 6

您希望在回复为是时继续运行循环，因此您需要一个回复变量。

public static void main(String [] args)
  {
    String reply = "yes";
    while(reply.equals("yes")) {
        // Create a Scanner object to read input.
        Scanner keyboard = new Scanner(System.in);

        //Get the user's name.
        System.out.print("What is your name?");
        String name = keyboard.nextLine();
        System.out.println("Hello there," + name);

        System.out.println("Would you like to enter another name? Please enter Yes Or No.");
        reply = keyboard.nextLine();
    }
  }
}

另外，请注意您不能使用reply == "yes"，因为这永远不会成立。这与String在内存中的含义有关。相反，请使用reply.equals("yes")。

循环使用Java（初学者）

6 个答案: