[Java] Switch / 자바 스위치

Java Switch Statements

Instead of writing many if..elsestatements, you can use the switch statement.

The switch statement selects one of many code blocks to be executed.

---

Syntax

switch(expression){
case x:
	//code block
case y:
	//code block
	break;
default:
	//code block
}

This is how it works?

• The switch expression is evaluated once.
• The value of the expression is compared with the values of each case.
• If there is a match**, the associated block of code is executed.**
• The break and default keywords are optional, and will be described later in this chapter.

---

Example

package Switch;

public class main {

	public static void main(String[] args) {
		
		int day = 4;
		switch (day){
			
		case 1:
			System.out.println("Monday");
			break;
		case 2:
			System.out.println("Tueseday");
			break;
		case 3:
			System.out.println("Wendsday");
			break;
		case 4:
			System.out.println("Thursday");
			break;
		case 5:
			System.out.println("Friday");
			break;
		case 6:
			System.out.println("Saturday");
			break;
		case 7:
			System.out.println("Sunday");
			break;
		}
	}
}

---

Break;

• When Java reaches a break keyword, it breaks out of the switch block.
• This will stop the execution of more code and case testing inside the block.
• When a match is found, and the job is done, it’s time for a break. There is no need for more testing.

---

The default Keyword

The default keyword specifies some code to run if there is no case match:

 

/*
 * The default Keyword
 */
package Switch;

public class main2 {
	public static void main(String[] args) {

		int day = 4;
		switch (day){
			
		case 1:
			System.out.println("Monday");
			break;
		case 2:
			System.out.println("Tueseday");
			break;
		case 3:
			System.out.println("Wendsday");
			break;
//		case 4:
//			System.out.println("Thursday");
//			break;
		case 5:
			System.out.println("Friday");
			break;
		case 6:
			System.out.println("Saturday");
			break;
		case 7:
			System.out.println("Sunday");
			break;
		default:
			System.out.println("Looking forward to the Weekend");
		}
	}
}

 

💡Note that if the default statement is used as the last statement in a switch block, it does not need a break.