Today, let's talk about the if branch statement of the selection structure

1. Single branch if Selection structure ：
    Grammatical structure ：
       if( Conditions ){
     // Code block
      }
    The law of execution ：
      If the condition is true, perform {} Block of code in , After executing the code block , Carry on {} Later code
        If the condition is false, Then skip if Selection structure , perform {} Later code
  Be careful ：
        No matter how simple or responsible the conditions are written , The final result should be Boolean , Either for true Either for false
The following is a small example to experience

public static void main(String[] args) {
		
//		 Chuangjie Scanner object 
		Scanner sc = new Scanner(System.in);
//		 Get results 
		System.out.println(" Enter grades ");
		double score = sc.nextDouble();
//		 Conditions for obtaining rewards 
		if(score>90){
			System.out.println(" good , You can get a Ferrari 3 RMB coupon ");
		}
		sc.close();// Turn off keyboard input 
	}

2.  Multiple branches if Select institutions
  Grammatical structure ：
     if( Conditions 1){
           // Code block 1;
      }else if( Conditions 2){
            // Code block 2;
         }else if( Conditions 3){
                  // Code block 3;
        }
         }else{
            Code block n;
        }
      The law of execution ：
            Judge the condition 1, If the condition 1 by true, Then execute the code block 1, After executing the code block 1, End the whole thing if-else-if structure , perform if-else-if The code behind the structure
      If the condition 1 by false, Then continue to judge the conditions 2, If the condition 2 by true, Then execute the code block 2, After executing the code block 2, End the whole thing if-else-if structure , perform if-else-if The code behind the structure
          If the condition 2 position false, Then continue to judge the conditions 3, If the condition 3 position true, Then execute the code block 3, After executing the code block 3, End the whole thing if-else-if structure , perform if-else-if The code behind the structure
          If the condition 3 by false, Continued to ......
          If all the conditions are not met , execute else{} Block of code in n

  Be careful ：
         （1） All conditions are Boolean
         （2）else if There can be many
        （3）else Yes, it can be omitted , When all conditions are not met , And there's no else When , Then the whole if-else-if The code in the structure will not be executed     
 

public static void main(String[] args) {
		
		/*
		 *  achievement >90, good 
		 *  achievement >80 <90, good 
		 *  achievement <60, fail, 
		 */
		Scanner sc = new Scanner(System.in);
		System.out.println(" Come on, come on , Tell me how many marks you got ：");
		double score = sc.nextDouble();
		if(score>90){
			System.out.println(" Excellent ");
		}
		else if(score>80&&score<90){
			System.out.println(" Click on the tongue , Not a coward ");
		}
		else{
			System.out.println(" cut , Enter the factory ！");
		}
		
	}

3. Let me introduce you with a topic if Nesting of

Use if Select the structure to sort the three integers , Output in the order from small to large .

import java.util.Scanner;

// Use if Select the structure to sort the three integers , Output in the order from small to large 
public class Demo03 {

	public static void main(String[] args) {
// establish scanner object 
		Scanner sc = new Scanner(System.in);
//		 Let you do three things 
		System.out.println(" Enter three different integers ");
		int num1=sc.nextInt();
		int num2=sc.nextInt();
		int num3=sc.nextInt();
		
		if(num1>num2){
			if(num2>num3){
				System.out.println(num1+">"+num2+">"+num3);
			}
			else if(num2<num3){
				System.out.println(num1+">"+num3+">"+num2);
			}
			else
			{
				System.out.println(num3+">"+num1+">"+num2);
			}
			
		}
		else//num1<num2
		{
			if(num1>num3){
				System.out.println(num2+">"+num1+">"+num3);
			}
			if(num3>num2){
				System.out.println(num3+">"+num2+">"+num1);
			}
			else{
				System.out.println(num2+">"+num3+">"+num1);
			}
			
		}
		
		
	}