面试题：switch语句能否作用在byte上,能否作用在long上,能否作用在String上？

约定不等于承诺〃 2022-08-05 02:38 135阅读 0赞

/\*\*  
 \* 问题：switch语句能否作用在byte上,能否作用在long上,能否作用在String上  
 \* 基本类型的包装类（如：Character、Byte、Short、Integer）  
 \*  
 \* 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

\*/

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，源代码示例：

package java基础题目;
    
    public class Test5 {
    	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);
    	}
    
    }

switch中可以是字符串类型,String(jdk1.7之后才可以作用在string上)，源代码示例：

package java基础题目;
    
    /*
     * 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 Test6 {
    	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);
    	}
    }

switch中可以是1.5枚举类型，源代码示例：

package java基础题目;
    /*
     * switch中可以是1.5枚举类型
     */
    //枚举三个量
    enum Signal{
    	GREEN,YELLOW,RED;
    }
    public class Test7 {
    	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);
    	}
    
    }