User interaction scanner usage Advanced Edition example

User interaction scanner

java.util.Scanner yes java5 New features , Can pass Scanner Class to get user input

Basic grammar ：

Scanner s=new Scanner（System.in）;

adopt Scanner Class next（） And nextLine（） Method to get the input string , We usually need to Use hasNext（） And hasNextLine（） Determine whether there is any input data .

• next（） and hasNext（） Method

  1. You must read valid characters before you can end the input

  2. Whitespace encountered before entering valid characters for ,next（） Method will automatically remove it

     ** Such as Input hello world The output is hello **

  3. Only after entering a valid character can the blank space entered after it be used as a separator or Terminator

  4. next（） Cannot get string with space

package com.zhang.scanner;

import java.util.Scanner;

public class Demo01 {
    
    public static void main(String[] args) {
    
        // Create a scanner object , For receiving keyboard data 
        Scanner scanner=new Scanner(System.in);
        System.out.println(" Use next Mode reception ：");

        // Determine whether the user has input string 
        if (scanner.hasNext()){
    
            // Use next Mode to receive 
            String str=scanner.next();// The program will wait for the user to input 
            System.out.println(" The output is ："+str);
        }
        // All belong to IO If the class of the stream is not closed all the time   Will always take up resources , To form a good habit, turn it off after use 
        scanner.close();
    }
}

Use next Mode reception ：
hello world
The output is ：hello

• nextLine（） and hasNextLine（）
  1. With Enter End of character in other words nextLine（） Method returns all the characters before enter
  2. Can get blank

package com.zhang.scanner;

import java.util.Scanner;

public class Demo02 {
    
    public static void main(String[] args) {
    
        // Receive data from keyboard 
        Scanner scanner=new Scanner(System.in);
        System.out.println(" Use nextLine Mode reception ：");
        // Judge whether there is any input 
        if (scanner.hasNextLine()){
    
            String str=scanner.nextLine();
            System.out.println(" The output is ："+str);
        }
        scanner.close();
    }
}

Use nextLine Mode reception ：
hello world
The output is ：hello world

package com.zhang.scanner;

import java.util.Scanner;

public class Demo03 {
    
    public static void main(String[] args) {
    

        // Receive data from keyboard 
        Scanner scanner = new Scanner(System.in);

        System.out.println(" Please input data ：");

        String str=scanner.nextLine();

        System.out.println(" The output is ：" + str);

        scanner.close();
    }
}

Please input data ：
I love you! China
The output is ： I love you! China

expand

package com.zhang.scanner;

import java.util.Scanner;

public class Demo04 {
    
    public static void main(String[] args) {
    
        Scanner scanner=new Scanner(System.in);

        // Receive data from keyboard 
        int i;
        float f=0.0f;
        System.out.println(" please enter an integer ：");
        // If ... that 
        if (scanner.hasNextInt()){
    
            i=scanner.nextInt();
            System.out.println(" Integer data ："+i);
        }else {
    
            System.out.println(" The input is not integer data ！");
        }
        System.out.println(" Please enter the decimal ：");
        if (scanner.hasNextFloat()){
    
            f=scanner.nextFloat();
            System.out.println(" Fractional data ："+f);
        }else {
    
            System.out.println(" Input is not decimal data ！");
        }

        scanner.close();
    }
}

please enter an integer ：
10.1
The input is not integer data ！
Please enter the decimal ：
Fractional data ：10.1

We can enter multiple numbers , And find the sum and the mean , Press enter to confirm each number entered , End the input and output the execution result by inputting non number

package com.zhang.scanner;

import java.util.Scanner;

public class Demo05 {
    
    public static void main(String[] args) {
    
        //  We can enter multiple numbers , And find the sum and the mean , Press enter to confirm each number entered , End the input and output the execution result by inputting non number 
        Scanner scanner=new Scanner(System.in);
        // and 
        double sum=0;
        // Calculate how many numbers are entered 
        int m=0;
        // Loop to see if there is any input , And sum up each time in it 
        while (scanner.hasNextDouble()){
    
            double x=scanner.nextDouble();
            m=m+1;//m++
            sum=sum+x;
            System.out.println(" You entered the number one "+m+" Data , The current result sum="+sum);
        }
        System.out.println(m+" The sum of the numbers is "+sum);
        System.out.println(m+" The average number is "+(sum/m));

        scanner.close();
    }
}

10
You entered the number one 1 Data , The current result sum=10.0
20
You entered the number one 2 Data , The current result sum=30.0
30
You entered the number one 3 Data , The current result sum=60.0
guyguy
3 The sum of the numbers is 60.0
3 The average number is 20.0