对一个 switch case 语句使用两个值

2022-01-19 00:00:00 switch-statement java

在我的代码中，程序会根据用户输入的文本执行某些操作.我的代码如下:

In my code, the program does something depending on the text entered by the user. My code looks like:

switch (name) {
        case text1: {
            //blah
            break;
        }
        case text2: {
            //blah
            break;
        }
        case text3: {
            //blah
            break;
        }
        case text4: {
            //blah
            break;
        }

但是，text1和text4里面的代码是一样的.因此，我想知道我是否有可能实现类似

However, the code inside cases text1 and text4 is the same. I was therefore wondering if it would be possible for me to implement something like

case text1||text4: {
            //blah
            break;
        }

我知道 || 运算符在 case 语句中不起作用，但我可以使用类似的东西.

I know that the || operator won't work in the case statement but is there something similar I can use.

推荐答案

您可以同时使用 CASE 语句，如下所示.

You can use have both CASE statements as follows.

  case text1: 
  case text4:{
            //blah
            break;
        }

查看此示例:代码示例计算特定月份的天数:

SEE THIS EXAMPLE:The code example calculates the number of days in a particular month:

class SwitchDemo {
    public static void main(String[] args) {

        int month = 2;
        int year = 2000;
        int numDays = 0;

        switch (month) {
            case 1:
            case 3:
            case 5:
            case 7:
            case 8:
            case 10:
            case 12:
                numDays = 31;
                break;
            case 4:
            case 6:
            case 9:
            case 11:
                numDays = 30;
                break;
            case 2:
                if (((year % 4 == 0) && 
                     !(year % 100 == 0))
                     || (year % 400 == 0))
                    numDays = 29;
                else
                    numDays = 28;
                break;
            default:
                System.out.println("Invalid month.");
                break;
        }
        System.out.println("Number of Days = "
                           + numDays);
    }
}

这是代码的输出:

Number of Days = 29

失败:

另一个有趣的地方是break语句.每个中断语句终止封闭的 switch 语句.控制流程继续switch 块之后的第一条语句.中断语句是必要的，因为没有它们，switch 块中的语句 会下降through:匹配case标签后的所有语句都在序列，无论后续案例标签的表达如何，直到遇到 break 语句.

Another point of interest is the break statement. Each break statement terminates the enclosing switch statement. Control flow continues with the first statement following the switch block. The break statements are necessary because without them, statements in switch blocks fall through: All statements after the matching case label are executed in sequence, regardless of the expression of subsequent case labels, until a break statement is encountered.

示例代码:

public class SwitchFallThrough {

    public static void main(String[] args) {
        java.util.ArrayList<String> futureMonths =
            new java.util.ArrayList<String>();

        int month = 8;

        switch (month) {
            case 1:  futureMonths.add("January");
            case 2:  futureMonths.add("February");
            case 3:  futureMonths.add("March");
            case 4:  futureMonths.add("April");
            case 5:  futureMonths.add("May");
            case 6:  futureMonths.add("June");
            case 7:  futureMonths.add("July");
            case 8:  futureMonths.add("August");
            case 9:  futureMonths.add("September");
            case 10: futureMonths.add("October");
            case 11: futureMonths.add("November");
            case 12: futureMonths.add("December");
            default: break;
        }

        if (futureMonths.isEmpty()) {
            System.out.println("Invalid month number");
        } else {
            for (String monthName : futureMonths) {
               System.out.println(monthName);
            }
        }
    }
}

这是代码的输出:

August
September
October
November
December

在 switch 语句中使用字符串

Using Strings in switch Statements

在 Java SE 7 及更高版本中，您可以在 switch 中使用 String 对象语句的表达式.以下代码示例，根据字符串的值显示月份的数字命名月份:

In Java SE 7 and later, you can use a String object in the switch statement's expression. The following code example, , displays the number of the month based on the value of the String named month:

public class StringSwitchDemo {

    public static int getMonthNumber(String month) {

        int monthNumber = 0;

        if (month == null) {
            return monthNumber;
        }

        switch (month.toLowerCase()) {
            case "january":
                monthNumber = 1;
                break;
            case "february":
                monthNumber = 2;
                break;
            case "march":
                monthNumber = 3;
                break;
            case "april":
                monthNumber = 4;
                break;
            case "may":
                monthNumber = 5;
                break;
            case "june":
                monthNumber = 6;
                break;
            case "july":
                monthNumber = 7;
                break;
            case "august":
                monthNumber = 8;
                break;
            case "september":
                monthNumber = 9;
                break;
            case "october":
                monthNumber = 10;
                break;
            case "november":
                monthNumber = 11;
                break;
            case "december":
                monthNumber = 12;
                break;
            default: 
                monthNumber = 0;
                break;
        }

        return monthNumber;
    }

    public static void main(String[] args) {

        String month = "August";

        int returnedMonthNumber =
            StringSwitchDemo.getMonthNumber(month);

        if (returnedMonthNumber == 0) {
            System.out.println("Invalid month");
        } else {
            System.out.println(returnedMonthNumber);
        }
    }
}

这段代码的输出是 8.

The output from this code is 8.

来自 Java 文档

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