Branch statement of process control

:::info
according to Forgetting curve ： If there is no record and review ,6 Days later, I will forget 75% The content of
Reading notes are a tool to help you record and review , Don't stick to form , Its core is ： Record 、 Look over 、 reflection
:::

Overview of process control statements

In the default program, it is a sequential structure , From top to bottom ; Use mind mapping , Structured core concepts .

Branch statement

if sentence （ The final judgment condition must be ： Boolean type value ）

1 Simple if Sentence format ：

Sentence format ：
if ( Judge the condition ){
Statement of body ; // If the judgment condition is true, execute the body of the statement ;
}

int nub1 = 1;
int nub2 = 2;
if(nub1>nub2){
    
       System.out.println(" Executed the body of the statement ");  // The judgment condition is false, This sentence does not execute ;
}

2 if…else Sentence format

Sentence format ：
if ( Judge the condition ){
Statement of body 1; // If the judgment condition is true, execute the body of the statement 1;
}else{
Statement of body 2; // If the judgment condition is not tenable, execute the body of the statement 2;
}

int nub1 = 1;
int nub2 = 2;
if(nub1>nub2){
    
       System.out.println(" Executed the body of the statement 1");  // The judgment condition is false, This sentence does not have an executive ;
}else{
    
       System.out.println(" Executed the body of the statement 2");  // The judgment condition is false, Execute this sentence ;
}

3 if…else if…else… Sentence format

Sentence format ：
if ( Judge the condition 1){
Statement of body 1; // If the judgment condition is true, execute the body of the statement 1;
}else if( Judge the condition 2){
Statement of body 2; // Judge the condition 1 Don't set up , Judge the condition 2 establish , Execute statement body 2;
}else{
Statement of body 3; // Judge the condition 1 and 2 No execution statement body 3;
}

/*  Exam rewards ：  fraction >=90: Reward a bike  90> fraction >=80: Reward the amusement park for a one-day trip  80> fraction : A good beating  */
public class IfTest {
    
    public static void main(String[] args) {
    
        int chengji;
        Scanner sc = new Scanner(System.in);
        System.out.println(" Please enter the grade ：");
           chengji = sc.nextInt();
           if (chengji <=100 && chengji>=0){
    
               if (chengji>=90){
    
                   System.out.println(" Congratulations ！ Reward a bike ！");
               }else if (chengji>=80 && chengji<90){
    
                   System.out.println(" Congratulations ！ Reward the amusement park for a one-day trip ！");
               }else{
    
                   System.out.println(" Come on, take a beating ！");
               }
           }else{
    
               System.out.println(" The score is wrong ！");
           }
    }
}

switch sentence

switch Sentence format ：
switch（）{
case 1：
Statement of body 1;
break;
case 2：
Statement of body 2;
break;
case 3：
Statement of body 3;
break;
.
.
.
default：
The default value is the body of the statement ;
break;

}

1 matters needing attention ：jdk Characteristics and week Value range of

• Basic types ：byte、short、int、long
• Reference type ：jdk5 Start , Enumeration types are allowed ;jdk7 Start , allow String
• jdk14 Start allowing , One case Followed by multiple values ：case 1,2,3:
• if And switch choose ： The judgment of scope is if; Fixed value judgment switch;

switch(week){
    
    case 1:
       //  Statement of body 1;
        break;
    case 2:
       //  Statement of body 2;
        break;
    case 3:
      //  Statement of body 3;
        break;
    default:
      //  Default statement body ;
        break;
}

2 case through （ You can optimize the code ）

case Penetration example ： If there are multiple repeated statement bodies, you can use case through

switch(week){
    
    case 1:
    case 2:
    case 3:
        // Repeat the sentence body ;
        break;
    default:
        break;
}

3 jdk14 New features in the future （ You can optimize the code ）

case Penetration example ： If there are multiple repeated statement bodies, you can use case through

switch(week){
    
    case 1,2,3:
        // Repeat the sentence body ;
        break;
    default:
        break;
}

Be careful ： The most commonly used logical operator in programming is ： Short circuit and （&&)、 Short circuit or （||） He Fei （！）; It can improve the operation efficiency of the code ;