技術標籤：Java基礎java

示例

package Base;

public class switchcase {
	public static void main(String[] args) {
		//第一種c/c++/java通用的形式
        String flag = "aaa";
        switch (flag) {
        case "aaa":
            System.out.println("Selected aaa");
            break;
        case
 
 "bbb":
            System.out.println("Selected bbb");
            break;
        case "ccc":
            System.out.println("Selected ccc");
            break;
        default:
            System.out.println("No flag selected");
            break;
        }
 

        
        //第二種java通用的新形式，不需要break,如果有多條語句，需要用{}括起來
        switch (flag) {
        case "aaa" -> System.out.println("Selected aaa");
        case "bbb" -> System.out.println("Selected bbb");
        case "ccc" -> {
        	System.out.
 
println("Selected ccc");
        	System.out.println("Good choice");
        }
        default -> System.out.println("No selected");
        }
        
        //第三中，java中帶有的返回值使用
        int opt = switch(flag) {
        case "aaa" -> 1;
        case "bbb" -> 2;
        case "ccc","ddd" -> 3;
        default -> 0;
        };
        System.out.println("opt = " + opt);
        
        //第四種，yield使用，帶有返回值
        flag = "red";
        opt = switch (flag) {
        case "aaa" -> 1;
        case "bbb", "ccc" -> 2;
        default -> {
            int code = flag.hashCode();
            yield code; // switch語句返回值
        }
        };
        System.out.println("opt = " + opt);
    };
}

執行結果