Java面试题：switch能否作用在byte、long、String上？

• switch可作用于char byte short int

• switch可作用于char byte short int对应的包装类

• switch不可作用于long double float boolean，包括他们的包装类

• switch中可以是字符串类型,String(JDK1.7之后才可以作用在string上)

• switch中可以是枚举类型(JDK1.5之后)

public class Test {
	public static void main(String[] args) {
		// switch可作用于char byte short int
		char season1 = 3;
		byte season2 = 3;
		short season3 = 3;
		int season4 = 3;
 
		// switch可作用于char byte short int对应的包装类
		Character season11 = 3;
		Byte season22 = 3;
		Short season33 = 3;
		Integer season44 = 3;
 
		// 下面的基本类型的包装类就不行了，还有double float的包装类
		// Long season = 0;
 
		// switch不可作用于long double float boolean，包括他们的包装类
		long season5 = 3;
		double season6 = 3;
		float season7 = 3f;
		boolean season8 = false;
 
		String strSeason = "";
		switch (season1) {
		case 1:
			strSeason = "Spring";
			break;
		case 2:
			strSeason = "Summer";
			break;
		case 3:
			strSeason = "Fall";
			break;
		case 4:
			strSeason = "Winter";
			break;
		default:
			strSeason = "四季中没有这个季节";
			break;
		}
		System.out.println("strSeason:" + strSeason);
	}
}

JDK1.5枚举

/*
 * switch中可以是1.5枚举类型
 */
//枚举三个量
enum Signal{
	GREEN,YELLOW,RED;
}
public class Test {
	public static void main(String[] args) {
		Signal color = Signal.RED;
		
		switch (color) {
		case RED:
			color = Signal.YELLOW;
			break;
		case YELLOW:
			color = Signal.RED;
		case GREEN:
			color = Signal.YELLOW;
		default:
			System.out.println("什么鬼灯");
			break;
		}
		
		System.out.println("color:"+color);
	}
}

JDK1.7之后支持String，但是要求case也是String

/*
 * switch中可以是字符串类型
 *String(jdk1.7之后才可以作用在string上)
 */
public class Test {
	public static void main(String[] args) {
		int season = 0;
		String strSeason = "Summer";
		switch (strSeason.toLowerCase()) {
		case "spring":
			season = 1;
			break;
		case "summer":
			season = 2;
			break;
		case "fall":
			season = 3;
			break;
		case "winter":
			season = 4;
			break;
		default:
			season = -1;// 没找到对应的季节
			break;
		}
		System.out.println(strSeason + "-->" + season);
	}
}