Loop structure -- while loop and do while loop

First of all, let's talk about the benefits of the next cycle ： The most obvious is to reduce the duplication and redundancy of code , Greatly improved efficiency

1.while loop

Grammatical structure ：
                  Initial value ;
                 while( The loop condition ){
                     // Loop operation code
                      Iteration part
                 }
               The law of execution ：
                 1） First, execute 1 Code of second initial recognition value
                 2） Judge cyclic condition , If the cycle condition is true, Is executed {} Inside the loop operation code and iteration part of the code , After iteration , Continue to return to judge the cycle condition , Decide whether to continue the cycle operation according to the result of the cycle condition
                  If the cycle condition is false, End the whole while Loop structure , So let's keep going while The code after the loop structure
            Be careful ：
                 1） The initial value code is executed only once
                 2） No matter how simple or complex it is written , The result can only be Boolean , Either for true Either for false
                 3） The function of the iteration part is to change the initial value , Let the cycle condition no longer be satisfied at a certain time , To end the whole while Loop structure
                 4)while Loop first judge , After execution

Let's take the simplest example ：

subject ： Output 100 Study hard and make progress every day

        int i =1;
		while(i<=100){//i<=100  The loop condition 
			System.out.println(" The first "+i+" All over ： study hard , Day day up .");// Cyclic operation 
			i++;// iteration ： The purpose of iteration is to change the initial value , In order to be at a certain moment , Let the cycle condition no longer be satisfied , End loop operation , If there is no iteration , The cycle goes into a dead cycle 
		}
		

2.do-while loop
             Grammatical structure ：
                 Initial value l;
                 do{
                      Cyclic operation
                      Iteration part
                 }while( The loop condition );
               The law of execution ：
               1） First, execute 1 Secondary initial value code
               2） Get into {} Internal execution 1 Loop operation and iteration part , Judge the condition after execution , If the condition is true, return {} Execute loop operation and iteration part in ,
                      If the condition is false, End the whole do-while Loop structure , So let's keep going do-while The code after the loop structure
            Be careful ：
              1） The initial value only executes 1 Time
              2） Cycle conditions, no matter how simple or complex they are written , Can only be Boolean , Either for true, Either for false
              3）do-while Loop is to execute a loop operation first , And then judge the cyclic condition , therefore , If the first judgment cycle condition is not satisfied , The loop operation will also be performed once （do-while The loop operation in the loop will be executed at least once ）

Still a small example

subject ：/ Use do-while Cyclic output 1-100 Value

		
		// Initial value 
		int i =1;
		do{
			System.out.println(i);// Cyclic operation 
			i++;// Iteration part 
		}while(i<=100);// The loop condition 

To sum up while and do-while The difference between

1） Execution order is different

2） When the initial condition does not meet the cycle conditions ：

while A loop will not execute

do-while The loop executes at least once in any case , To put it simply , Don't worry about anything. Let's run the cycle again first ！