3.1.4 switch structure

1. switch(){
   case:
   break;
   case:
   break:
   default:
   break;
   }

2. Code Example: Judging that a random letter is a vowel or consonant

/**
 * Test the use of switch statements
 * @author Wang Li Sheng
 *
 */
public class testSwitch {
	public static void main(String[] args){
		

		//Testing vowels or consonants of letters
			char c='a';
			int rand=(int)(26*Math.random());
			char c2=(char)(c+rand);
			System.out.println("The letter is:"+c2);
			
			switch (c2){
			case 'a':
			case 'e':
			case 'i':
			case 'o':
			case 'u':
				System.out.println("vowel");
				break;
			case 'y':
			case 'w':
				System.out.println("Half vowel");
				break;
			default:
				System.out.println("consonant");			
		
		}
	}

}

Note: In the switch statement, variables cannot be defined after the break statement

3.2.1 Use of while

1. Structure:
   

2. While{
   ...
   You have to change the conditional statement, otherwise the dead cycle
   }

3. Code example: Calculate the sum from 0 to 100 and:

/**
 * Testing the Use of While Statements
 * 
 * @author Wang Li Sheng
 *
 */
public class testWhile {
   public static void main(String[] args){
	   
	   //Calculate the value of 1+2+3+...+100
	   
	   int i=1;
	   int sum=0;
	   
	   while(i<=100){
		   sum=sum+i;
		   i++;
	   }
	   System.out.println("And:"+sum);
   }
}

3.2.2 DO-WHILE cycle
Functions are the same as while
The difference is: do-while executes the loop first, and then judges.

3.2.3 for cycle

1. For (Defining initial variables; Judging conditions; Changing conditional variables){
   }
   Note: When defining a trial variable, if there are two variables, you only need to use an int.

Code example:

/**
 * Test for loop structure
 * 
 * @author Wang Li Sheng
 *
 */
public class testFor {
  public static void main(String[] args){
	  
	  //Training 1: Calculate the sum of 1 to 100
	  int sum=0;
	  for(int i=1;i<=100;i++){
		  sum+=i;
	  }
	  System.out.println("sum="+sum);
	  
	  //Training 2: Output 90 to 1 multiples of all 3
	  for (int i=90;i>=1;i=i-3){
		  System.out.print(i+",");
	  }
	  
	  //Training 3: Values of output data for i and j
	  for (int i=1,j=i+6;i<=5;i++,j=i*2){
		  System.out.println("i="+i+"j="+j);
	  }  
  }
}

Output: