Java Eclipse 控制台在比较用户输入值和字符串值之前终止程序

Question

所以我正在为我的弟弟制作这个程序，我遇到了一个问题。该程序假设请求用户的输入，然后通过一系列"if"语句将其与多个字符串值进行比较。相反，发生的情况是用户提供他们的输入，然后程序立即终止。我已经在这里待了几个小时，我开始对此感到非常兴奋。这是我到目前为止键入的代码：

package package1;
import java.util.Scanner;
public class Psychic_Calculator {
@SuppressWarnings("resource")
public static void main(String[] args) {
Scanner scan = new Scanner(System.in);  
System.out.println("Hello user, please type your name below:"); 
String a = scan.nextLine();
System.out.println("Welcome " + a + ", think of a number. Once you have your  number, type 'okay' below!");
String b = scan.nextLine();
if (b == "okay"){
System.out.println("Now, add '11' to your number and type 'okay' below.");
    }
else if (b == "Okay"){
System.out.println("Please don't capitalize 'okay', try typing it again!");
String c = scan.nextLine();
if (c == "okay"){
System.out.println("Now, add '11' to your number and type 'okay' below.");
String d = scan.nextLine();
if (d == "okay"){
System.out.println("Now, add '2' to your new number, then type 'okay' below.");
String e = scan.nextLine();
if (e == "okay"){
System.out.println("Now, subtract your original number from your new number, then type 'okay' below.");
String f = scan.nextLine();
if (f == "okay"){
System.out.println("Your new number is '13'. Don't even try denying it.");
                    }
                }
            }
        }
        if (c == "Okay"){
        System.out.println("I already told you not to capitalize 'okay', try typing it again, you idiot!");
        String g = scan.nextLine();
        if (g == "okay"){
        System.out.println("Now, add '11' to your number and type 'okay' below.");
        String h = scan.nextLine();
        if (h == "okay"){
        System.out.println("Now, add '2' to your new number, then type 'okay' below.");
        String i = scan.nextLine();
        if (i == "okay"){
        System.out.println("Now, subtract your original number from your new number, then type 'okay' below.");
        String j = scan.nextLine();
        if (j == "okay"){
        System.out.println("Your new number is '13'. Don't even try denying it.");  
                        }
                    }
                }
            }
        }
        if (c != "okay") {
        while (c != "okay") {
        System.out.println("Do you even know how to spell 'okay'?" + "'" + c + "' does not spell 'okay', you moron! Try typing 'okay' again.");
        String n = scan.nextLine();
        if (n == "okay"){
        System.out.println("Finally, you learned how to spell 'okay'. Your vocabulary is now one word larger, you're welcome. Now, please add '11' to your number and then type 'okay'(correctly this time).");
        String k = scan.nextLine();
        if (k == "okay"){
        System.out.println("Now, add '2' to your new number, then type 'okay' below.");
        String l = scan.nextLine();
        if (l == "okay"){
        System.out.println("Now, subtract your original number from your new number, then type 'okay' below.");
        String m = scan.nextLine();
        if (m == "okay"){
        System.out.println("Your new number is '13'. Don't even try denying it.");  
                }
                }
            }
        }
        else {
            System.out.println(a + ", " + "you have failed to type 'okay' too many times! You have no idea how to spell 'okay' you electricutin' motherboarder! Go shove your face in a pile of computer chips and grow a pair!");
                    System.out.println("(of RAM cartriges...I meant to say RAM cartriges).");
                }   
             }
          }
       }
    }
}

Answer 1

问题在于你如何比较字符串。将b == "okay"更改为b.equals("okay")将所有==比较更改为 .equals() 或 .equalsIgnoreCase() 。对于否定，请使用(!(c.equals("okay"))

在 Java 中，==将按值比较基元类型，但会按内存地址比较对象。换句话说，当你说b == "okay"它不做值比较时，它会检查这两个对象是否指向相同的内存地址，这当然是错误的。

更新：只是关于你编写这个程序的方式的一些事情。

1）你正在不必要地创建很多字符串对象。你最好重用一个字符串对象，直到你绝对需要另一个字符串对象。这适用于您正在使用的任何对象。尽量不要不必要地分配对象。2）代替所有的if语句，你可以定义一个指令数组，就像这样并压缩你的代码：

String [] instr = {"Add 2", "Add 11", "Subtract Original"};//array of directions
String [] invalidResp = {"Wrong", "You can't spell", "Try Again", "No"};//array of responses to print if user doesnt type 'okay' properly
int instrCounter = 0;//you don't really need this but it helps with readability
String userInput = "";//only string object you'll need =)
while (instrCounter < instr.length){//I couldve just as easily used a for loop instead.
   userInput = scan.nextLine();
   while (!userInput.equals("okay")){
      userInput = scan.nextLine();
      System.out.println(invalidResp[(int)   (Math.random()*invalidResp.length)]);
   //will print a random invalid response from the invalidResp array
      System.out.println(userInput + " is not how you spell okay");
   }//end while
   System.out.println("Great, now, " + instr[instrCounter]);
   instrCounter++;
}//end outer while

请记住，当你编写代码时，你希望它是相当通用和灵活的。我编写代码的方式，我可以添加到 instr 数组或添加更多无效响应，并且不会不必要地创建对象。就像我在内联评论中所说的那样，我可以很容易地将 for 循环用于外部循环，但为了可读性并确保您理解我在做什么，我使用了 while 循环，因为我相信它们更直观地阅读。

Answer 2

游戏： 而（运行） { System.out.println（"---------------------------"）;

继续游戏;

命名 while 循环，然后就可以中断; out。