If the cycle condition is true, Execute a circular statement; Otherwise, end the cycle.

expression 1: Used to initialize loop variables.

Expression 2: loop condition.

Expression 3: update loop variable.

Example 1: calculate the factorial of 5.

int result = 0; 
for (int i = 1; i <= 5; i++) { 
 result *= i; 
} 
System.out.println("result = " + result);

Example 2: calculation 1+ 2! + 3! + 4! + 5!

int sum = 0; 
for (int i = 1; i <= 5; i++) { //The number of external circulation is five as required
 int tmp = 1; 
 for (int j = 1; j <= i; j++) { //Find the factorial of each number in the inner loop
 tmp *= j; 
 } 
 sum += tmp; 
} 
System.out.println("sum = " + sum);

(error prone point of this question: when defining tmp, remember to put it outside the inner loop and in the outer loop. If it is placed outside the outer loop, tmp will only be initialized once, and there will be problems in subsequent factorization, so we can't get the desired results.)

Execute the loop statement first , Then determine the cycle conditions. (some people get on the bus first and then make up the ticket / / it's like cutting first and playing later)

Example: print 1 ~ 10.

int num = 1; 
do { 
 System.out.println(num); 
 num++; 
} while (num <= 10); 

Note: don't forget the semicolon at the end of the do...while loop. Generally, do while uses less, while and for loops use the most.

6, Special statements in a loop

1. break statement

int num = 100; 
while (num <= 200) { 
 if (num % 3 != 0) { 
 num++;
 continue; 
 } 
 System.out.println("A multiple of 3 was found, by:" + num); 
 num++; 
}

7, Input and output in Java

1. Output

This is also mentioned in the first section of getting to know Java. There are three kinds of output in Java.

2,System.out.print("hello world");    // Output a string without line breaks

3,  int a=77;

       System.out.printf("a=%d\n"，a);     // As in c, format the output.

 

How can it end?

 

Guess numbers games

Finally, write a guessing game to end this article~

Expand the usage of random (also import util package before use)——

 

import java.util.Random; 
import java.util.Scanner;
class Test { 
 public static void main(String[] args) { 
 Random random = new Random(); 
 Scanner sc = new Scanner(System.in); 
 int guess = random.nextInt(100); 
 while (true) { 
     System.out.println("Please enter the number you want to enter: (1-100)"); 
     int num = sc.nextInt(); 
         if (num < guess) { 
             System.out.println("Low"); 
         } else if (num > guess) { 
             System.out.println("High"); 
         } else { 
             System.out.println("You guessed right"); 
             break; 
         } 
     } 
  } 
}

  The final running result is:

  Isn't it very interesting? After learning the loop and logic, you can write more interesting games.

The next article is about the use of methods (functions). I really think I'm so slow to write. Hahaha

to be continue →

Welcome to discuss and exchange with each other. Welcome to catch insects!