Java program flow control example tutorial

Java Program Flow Control

This article separately organizes the knowledge points of loop structures:

As mentioned before, loop structures are divided into: for loop, while loop, do...while Loops are the three most basic loop structures; versions after JDK 1.5 also provide a foreach loop for traversing arrays and collections.

The four components of the loop statement:

• Initialization part

• Loop condition part

• Loop body part

• Iteration part

for loop:

for (initialization condition; loop condition; iteration part){

Loop body

}

1 public class TestFor {2     public static void main(String[] args) {3         //基础for循环，讲一个语句打印多次4         for(int i=0; i

Exercise: Print 1-100 All even numbers

 1 public class TestFor { 2     public void PrintNum(){ 3         for(int i=1; i0 5                 System.out.println("i="+i); 6             } 7         } 8     } 9     public static void main(String[] args) {10         TestFor testFor = new TestFor();11         testFor.PrintNum();12     }13 }

Exercise: Write code to loop from 1 to 150 and print a value in each line. In addition, you need to print "foo" in each line that is a multiple of 3, in Print "biz" on every line that is a multiple of 5,

Print "baz" on every line that is a multiple of 7

 1 public class TestFor { 2     public void FooBizBaz(){ 3         for(int i=1; i

Note: Must It should be noted that else if(){} cannot be used in this question. Once used, it will be impossible to print three fields at the same time in the number of lines that meet the multiples of 3, 5, and 7 at the same time, because once one of them meets the judgment condition, it will not Execute the if judgment statement below to directly jump out of the current loop and execute the next loop.

There are also many small basic for loop algorithms, such as printing the sum of all odd numbers from 1 to 100, printing out all the narcissus numbers (you can search for the daffodil numbers yourself), these questions can Practicing on your own will help strengthen your understanding of the for loop, so I won’t go into details here.

while loop:

　Initialization condition

while (loop condition){

Loop body

Iteration condition

}

Example: Output all even numbers within 1-100

 1 public class TestWhile { 2     public void evenNum(){ 3         int i = 1; //初始化条件 4         while(i

Note: The for loop and the while loop can be transformed into each other, because they have the same four parts, but the four parts are placed in different positions.

Another looping method of while loop:

do...while loop:

Initialization conditions

##do{

Loop body

Iteration condition

}while( Loop condition);

It can be seen from the above structure that the do...while loop first performs a loop to determine whether the loop condition is satisfied. If it is satisfied, Proceed to the next cycle, and stop the cycle if it is not satisfied.

Example: Print all even numbers from 1-100

 1 public class TestDoWhile { 2     public void evenNum(){ 3         int i = 1; 4         do{ 5             if(i % 2 == 0){ 6                 System.out.println("i="+i); 7             } 8             i++; 9         }while(i <div class="cnblogs_code">
<p style="margin-left: 30px"><span style="color: #0000ff">do...while和while循环的区别：</span></p>
<p style="margin-left: 30px"><span style="color: #0000ff">do...while循环中 初始化条件即使不满足循环条件也会直接执行一次循环体再进行循环条件判断，所以循环体至少被执行一次，而while循环是必须满足循环条件才会执行循环体。</span></p>
<h2 id="span-style-color-嵌套循环-span"><span style="color: #000000">嵌套循环</span></h2>
<p><span style="color: #000000">　　<strong>顾名思义,嵌套循环就是再一个循环中还能再声明一个循环</strong></span></p>
<p><strong><span style="color: #000000">　　几种嵌套方式：</span></strong></p>
<p><strong><span style="color: #000000">　　1.for循环中能够嵌套一个for或多个for；</span></strong></p>
<p style="margin-left: 30px"><strong><span style="color: #000000">2.while循环中可以嵌套一个或多个while循环；</span></strong></p>
<p style="margin-left: 30px"><strong><span style="color: #000000">3.for循环中可以嵌套一个或多个while循环；</span></strong></p>
<p style="margin-left: 30px"><strong><span style="color: #000000">4.while循环中可以嵌套一个或多个for循环；</span></strong></p>
<p style="margin-left: 30px"><strong><span style="color: #000000">5.for循环中可以嵌套一个或多个for/while循环；</span></strong></p>
<p style="margin-left: 30px"><strong><span style="color: #000000">6.while循环中可以嵌套一个或多个for/while循环。</span></strong></p>
<p style="margin-left: 30px"><strong><span style="color: #000000">示例：</span></strong></p>
<p style="margin-left: 30px"><strong><span style="color: #000000">For之间嵌套</span></strong></p>
<div class="cnblogs_code"><pre class="brush:php;toolbar:false"> 1 public class TestForFor { 2     /*打印出 ***** 3      *     ***** 4      *     ***** 5      *     ***** 6      *      */ 7     public void forQianTao(){ 8         for(int i = 1; i