JAVA-Scanner object advanced

JAVA-Scanner object

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Basic syntax Scanner s =new Scanner(System.in)

Get the input string through the next() and nextLine() methods of the Scanner class. Before reading, we generally need to use hasNext() and hasNextLine() to determine whether there is still input data.

next

import java.util.Scanner;

public class Demo1 {
    
    
    public static void main(String[] args) {
    
    

        //创建一个扫描器对象，用于接收键盘数据
        Scanner scanner = new Scanner(System.in);

        System.out.println("使用next方式接收：");

        //判断用户有没有输入字符串
        if(scanner.hasNext()==true){
    
    
            String str=scanner.next();
            System.out.println("输出的内容为："+str);

            //凡是属于IO流的类如果不关闭会一直占用资源，要养成好习惯用完就关。
            scanner.close();
        }

    }
}
**

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NextLine

import java.util.Scanner;

public class Demo2 {
    
    
    public static void main(String[] args) {
    
    
        Scanner scanner = new Scanner(System.in);
        System.out.println("使用nextLine方式接收");

        if(scanner.hasNextLine()){
    
    
            String str =scanner.nextLine();
            System.out.println("输出的内容为："+str);
        }
        scanner.close();
    }
}

input Output

import java.util.Scanner;

public class Demo3 {
    
    
    public static void main(String[] args) {
    
    
        Scanner scanner = new Scanner(System.in);
        System.out.println("请输入数据");


        String str =scanner.nextLine();
        System.out.println("输出的内容为："+str);

        scanner.close();
    }
}

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Advanced scanner

import java.util.Scanner;

public class Demo4 {
    
    
    public static void main(String[] args) {
    
    
        Scanner scanner = new Scanner(System.in);

        //从键盘接收数据
        int i=0;
        float f=0.0f;

        System.out.println("请输入整数：");
        //如果。。那么
        if(scanner.hasNextInt()){
    
    
            i=scanner.nextInt();
            System.out.println("整数数据："+i);
        }
        else
        {
    
    
            System.out.println("输入的不是整数数据！");
        }
        System.out.println("请输入小数：");
        //如果。。那么
        if(scanner.hasNextFloat()){
    
    
            f=scanner.nextFloat();
            System.out.println("小数数据："+f);
        }
        else
        {
    
    
            System.out.println("输入的不是小数数据！");
        }
    }
}

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import java.util.Scanner;

public class Demo5 {
    
    
    public static void main(String[] args) {
    
    
        //我们可以输入多个数字，并求其总和，每输入一个数字用回车确认，通过输入非数字来结束并输出执行结果；
        Scanner scanner = new Scanner(System.in);

        //和
        double sum=0;

        //计算输入了多少个数字
        int m=0;

        //通过循环判断是否还有输入，并在里面对每一次进行求和和统计
        while (scanner.hasNextDouble()){
    
    
            double x=scanner.nextDouble();
            m=m+1;
            sum=sum+x;
            System.out.println(m+"个数的和为："+sum);
        }
        System.out.println(m+"个数的和为："+sum);
        System.out.println(m+"个数的平均值为："+(sum/m));
        scanner.close();
    }
}