Java13 - Switch 开关语句
Java 12 将表达式引入 Switch 语句并作为预览功能发布。 Java13 添加了一个新的 yield 结构来从 switch 语句返回一个值。 它仍然是一个预览功能。
考虑以下示例 −
ApiTester.java
示例
public class APITester {
public static void main(String[] args) {
System.out.println("Old Switch");
System.out.println(getDayTypeOldStyle("Monday"));
System.out.println(getDayTypeOldStyle("Saturday"));
System.out.println(getDayTypeOldStyle(""));
System.out.println("New Switch");
System.out.println(getDayType("Monday"));
System.out.println(getDayType("Saturday"));
System.out.println(getDayType(""));
}
public static String getDayType(String day) {
var result = switch (day) {
case "Monday", "Tuesday", "Wednesday","Thursday", "Friday" -> yield "Weekday";
case "Saturday", "Sunday" -> yield "Weekend";
default -> "Invalid day.";
};
return result;
}
public static String getDayTypeOldStyle(String day) {
String result = null;
switch (day) {
case "Monday":
case "Tuesday":
case "Wednesday":
case "Thursday":
case "Friday":
result = "Weekday";
break;
case "Saturday":
case "Sunday":
result = "Weekend";
break;
default:
result = "Invalid day.";
}
return result;
}
}
编译并运行程序
$javac -Xlint:preview --enable-preview -source 13 APITester.java $java --enable-preview APITester
输出
Old Switch Weekday Weekend Invalid day. New Switch Weekday Weekend Invalid day.