javaswitch用法温度(javaswitch的用法)

Java Switch语句的用途和基本语法

在Java编程中，Switch语句是一种非常重要的控制流程语句，它常用于根据不同的条件选择不同的代码执行路径。Switch语句的基本语法是：在Switch关键字后面的括号中指定判断表达式，然后使用花括号{}来包含一系列的Case分支语句，根据判断表达式与每个Case分支的匹配结果来执行相应的代码。举个例子，下面的代码展示了一个简单的Switch语句，根据输入的数字选择相应的月份：

public class MonthName {
    public static void main(String[] args) {
        int month = 8;
        String monthString;
        switch (month) {
            case 1:  monthString = "January";
                     break;
            case 2:  monthString = "February";
                     break;
            case 3:  monthString = "March";
                     break;
            case 4:  monthString = "April";
                     break;
            case 5:  monthString = "May";
                     break;
            case 6:  monthString = "June";
                     break;
            case 7:  monthString = "July";
                     break;
            case 8:  monthString = "August";
                     break;
            case 9:  monthString = "September";
                     break;
            case 10: monthString = "October";
                     break;
            case 11: monthString = "November";
                     break;
            case 12: monthString = "December";
                     break;
            default: monthString = "Invalid month";
                     break;
        }
        System.out.println(monthString);
    }
}

Java Switch语句中多个Case分支的合并

在Java Switch语句使用时，如果存在一些Case分支有相同的代码执行路径，那么可以将这些Case分支合并，避免代码重复。下面的代码展示了如何使用Switch语句将英文星期几转换成数字：

public class WeekdayNumber {
    public static void main(String[] args) {
        String weekday = "Wednesday";
        int weekdayNumber;
        switch (weekday) {
            case "Monday":    weekdayNumber = 1; break;
            case "Tuesday":   weekdayNumber = 2; break;
            case "Wednesday": weekdayNumber = 3; break;
            case "Thursday":  weekdayNumber = 4; break;
            case "Friday":    weekdayNumber = 5; break;
            case "Saturday":  weekdayNumber = 6; break;
            case "Sunday":    weekdayNumber = 7; break;
            default:          weekdayNumber = -1; break;  
        }
        System.out.println(weekdayNumber);
    }
}

Java Switch语句中的枚举类型用法

在Java编程语言中，枚举类型是一种定义固定数量的已命名值的通用机制，Switch语句可以很方便的与枚举类型一起使用。例如，下面的代码展示了如何使用Switch语句和枚举类型来计算各个方向的向量值：

public enum Direction {
    UP, DOWN, LEFT, RIGHT
}

public class DirectionSwitch {
    public static void main(String[] args) {
        Direction direction = Direction.LEFT;
        int x = 0, y = 0;
        switch (direction) {
            case UP:    y--; break;
            case DOWN:  y++; break;
            case LEFT:  x--; break;
            case RIGHT: x++; break;
            default:         break;  
        }
        System.out.println("x: " + x + ", y: " + y);
    }
}