如何比较字符串

Question

我试图将其带到用户按下数字的位置，然后他们输入他们想要查看的可用选项的字符串。到目前为止，一切正常，除了当用户输入字符串时，它没有给出首选输出.. *显示电子邮件而不是颜色、用户 ID 等。这是我的代码.. 再次感谢！public static void printStuff(Record[] objects) {   Scanner in = new Scanner(System.in);   System.out.println("Enter the number and record name you would like to see");   int x = in.nextInt();   String bean = in.next();        if (x == 1 || x == 2 || x == 3 || x == 4 || x == 5 && bean.equals("email")) {            System.out.println(objects[x].getEmail());        }       else if (x == 1 || x == 2 || x == 3 || x == 4 || x == 5 && bean.equals("name")) {            System.out.println(objects[x].getfirstName());        }       else if (x == 1 || x == 2 || x == 3 || x == 4 || x == 5 && bean.matches("last name")) {            System.out.println(objects[x].getlastName());        }       else if (x == 1 || x == 2 || x == 3 || x == 4 || x == 5 && bean.matches("balance")) {            System.out.println(objects[x].getBalance());        }       else if (x == 1 || x == 2 || x == 3 || x == 4 || x == 5 && bean.matches("color")) {            System.out.println(objects[x].getColor());        }       else if (x == 1 || x == 2 || x == 3 || x == 4 || x == 5 && bean.matches("idnumber")) {            System.out.println(objects[x].getnumID());        } }

Answer 1

尝试一下，始终避免重新输入案例并使您的代码更加高效。

public static void printStuff(Record[] objects) {

   Scanner in = new Scanner(System.in);

   System.out.println("Enter the number and record name you would like to see");

   int x = in.nextInt();

   String bean = in.next();

        if (x >= 1 && x =< 5 ) {

            if (bean.equals("email"))

               System.out.println(objects[x].getEmail());

            else if (bean.equals("name"))

               System.out.println(objects[x].getfirstName());

            else if (bean.matches("last name"))

               System.out.println(objects[x].getlastName());

            else if (bean.matches("balance"))

               System.out.println(objects[x].getBalance());

            else if (bean.matches("color"))

               System.out.println(objects[x].getColor());

            else if (bean.matches("idnumber"))

               System.out.println(objects[x].getnumID());

        }

 }

Answer 2

在所有 if 条件中，&&的优先级高于||，因此必须将条件更改为：

(x == 1 || x == 2 || x == 3 || x == 4 || x == 5) && bean.equals("email").

这对应于您想要的逻辑，如果x1 到 5 中的某个值 AND bean 等于"email"。但是，请研究比较运算符，因为您可以将其简化为：

(1 <= x && x <= 5) && bean.equals("email").

Answer 3

也许更容易阅读：

if (1 <= x && x <= 5) {

    switch (bean) {

        case "email": 

            System.out.println(record.email);

            break;

        case "name": 

            System.out.println(record.firstName);

            break;

        ...

    }

}

使用switch 表达式(Java 13, --enable-preview)：

if (1 <= x && x <= 5) {

    System.out.println(switch (bean) {

        case "email" -> record.email;

        case "name" -> record.firstName;

        case "last name"-> record.lastName;

        ...

        default -> "unrecognized " + bean;

        // default -> throw new IllegalArgumentException(...);

    });

}

或者，如果对未知不执行任何操作bean：

if (1 <= x && x <= 5) {

    switch (bean) {

        case "email" -> System.out.println(record.email);

        case "name" -> System.out.println(record.firstName);

        ...

    }

}