Completely master JAVA process control

This article brings you relevant knowledge about java, which mainly introduces related issues about process control, including input and output, branch statements and loop statements, etc. I hope it will be helpful to you. Everyone is helpful.

## Recommended study: "

java video tutorial"

Process control

JAVA input and output

Input

##Two input methods:

Method 1: java.util.Scanner

The code is as follows:

public class a {
    public static void main(String[] args) {
        var sc = new Scanner(System.in);
        System.out.println("请输入姓名：");
        String name = sc.nextLine();
        System.out.printf("%n欢迎你：%s", name);
    }}

Generate a Scanner object, output "Please enter your name:", return the input string and assign it to name, output "%nWelcome %s" where %n means line break %s means name

Result:

Method 2: JOptionPane input content is confirmed As for string values, as long as they are not determined, they are all null

public class a {
    public static void main(String[] args) {
        String w = JOptionPane.showInputDialog("请输入词汇：");
        System.out.println(w);
    }}

Result:

Output

Three methods of outputting on the console

Method one: System.out.print(); Output to the console

Method two: System.out.println(); Output to the console and wrap
Method 3: System.out.printf(); format the output to the console

Code demonstration:

The first method is direct without line breaks Output

public class a {
    public static void main(String[] args) {
        int w = 1;
        int a = 2;
        System.out.print(w);
        System.out.print(a);
    }}

Result:

Second line break output

public class a {
    public static void main(String[] args) {
        int w = 1;
        int a = 2;
        System.out.println(w);
        System.out.println(a);
    }}

Result:

The third formatted output

%d means an int type variable, which means replacing the first %d with the value of w and the second %d with the value of a

public class a {
    public static void main(String[] args) {
        int w = 1;
        int a = 2;
        System.out.printf("w=%d a=%d", w, a);
    }}

Result:

branch statement

if else

## if() The condition in the brackets will return true as long as it is correct, and false if it is wrong

else means otherwise

public class a {
    public static void main(String[] args) {
       if (1>2){
           System.out.println("A");
       }else {
           System.out.println("B");
       }
    }}

Multiple judgments are as follows: First judgment If not, proceed to the next judgment, execute it when the return value is true, otherwise execute else

public class a {
    public static void main(String[] args) {
        if (1 > 2) {
            System.out.println("A");
        } else if (1 > 0) {
            System.out.println("B");
        } else {
            System.out.println("C");
        }
    }}

switch case default

switch multi-branch switch Statement

switch(w) The w in the brackets is the judgment parameter, and the number after case is the value matching w. When the value of w matches the value after the case, the statement in the current case is executed

break means to exit the current judgment, which means that there is no need to judge again later

default means the default value, when there is no match The default is this

public class a {
    public static void main(String[] args) {
        int w=1;
        String wk = "";
        switch (w) {
            case 2:
                wk = "星期一";
                break;
            case 3:
                wk = "星期二";
                break;
            case 4:
                wk = "星期三";
                break;
            case 5:
                wk = "星期四";
                break;
            case 6:
                wk = "星期五";
                break;
            case 7:
                wk = "星期六";
                break;
            default:
                wk = "星期日";
                break;
        }
        System.out.println(wk);
    }}

result:

Loop statement

for

for ( int i = 0; i 5

public class a {
    public static void main(String[] args) {
        for (int i = 0; i <p> Result: </p>

for in

for in is mainly used to loop collections Or an array, use an array to demonstrate

public class a {
    public static void main(String[] args) {
        int[] a = {1, 2, 3, 4, 5};
        for (int i : a) {
            System.out.println(i);
        }
    }}

i corresponds to the value in the table below of array a, which is equivalent to looping output a[0],a[1]a[2],a [3]The value of a[4]

while do while

while(condition){}

Execute the statement if the conditions are met, exit if not.

• 
  

  public class a {
      public static void main(String[] args) {
          int i = 0;
          while (i 

Result:

do while

Different from while, do while is executed once and then judged

public class a {
    public static void main(String[] args) {
        int i = 0;
        do {
            i++;
            System.out.println(i);

        } while (i <br>The output is executed first and then judged. Therefore, the condition i<blockquote><p> result: </p></blockquote><p></p><h3 id="break-continue">break continue</h3><blockquote><p><strong>break;</strong> 终止当前循环语句<br><strong>continue;</strong> 结束这一次循环，立即准备开启下一次循环</p></blockquote><pre class="brush:php;toolbar:false">int i = 0;while (++i  10) break;}

当i被2整除就跳过这一次，进行下一次循环。当i大于10就结束循环。

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