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

所以我在为我弟弟和我运行制作这个程序时遇到了问题。该程序假设要求用户输入，然后通过一系列 "if" 语句将其与多个字符串值进行比较。相反发生的是用户提供他们的输入，然后程序立即终止。我已经为此工作了几个小时，并且开始对此感到非常恼火。这是我到目前为止输入的代码：

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

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

在Java中，==将按值比较原始类型，但会按内存地址比较对象。换句话说，当你说 b == "okay" 它不是在进行值比较时，它是在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：关于您编写此程序的方式的一些事情。

1) 您不必要地创建了很多字符串对象。在绝对需要另一个字符串对象之前，最好重新使用一个字符串对象。这适用于您正在使用的任何对象。尽量不要分配不必要的对象。 2) 除了所有的 if 语句，您可以定义一个指令数组，像这样并压缩您的代码：

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，当您编写代码时，您希望它相当通用和灵活。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，并且我不会不必要地创建对象。就像我在内联评论中所说的那样，我本来可以很容易地为外循环使用 for 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，因为我相信它们是阅读起来更直观。

Answer 2

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

继续游戏；

//命名while循环然后你就可以break了；出。

Java Eclipse 控制台在比较用户输入值和字符串值之前终止程序

Java Eclipse console terminates program before comparing values of user input and string value

string

compare

input