Scanner

1.
public class Demo01 {
    public static void main(String[] args) {

        //创建一个扫描器对象 用于接受键盘数据
        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()){
            String str= scanner.next();
            System.out.println("输入的内容为："+str);
        }

        //IO流的类如果不关闭会一直占用资源，要养成用完关闭的习惯

        scanner.close();
    }
2.
Public class Demo02 {

    public static void main(String[] args) {        //从键盘接收数据

        Scanner scanner = new Scanner(System.in);
        System.out.println("使用nextline的方式接收:");
        //判断是否还有输入
        if (scanner.hasNextLine()){
            String str= scanner.nextLine();
            System.out.println("输入的内容为："+str);



        }


        scanner.close();
    }
3.

public class Demo03 {

    public static void main(String[] args) {
        Scanner scanner = new Scanner(System.in);
        System.out.println("请输入内容");
        String str=scanner.nextLine();
        System.out.println("输出的内容为:"+str);
        scanner.close();
    }
4.

public class Demo05 {
    public static void main(String[] args) {
        Scanner scanner = new Scanner(System.in);
        double sum =0;
        int m=0;
        while (scanner.hasNextDouble()){
             double x=scanner.nextDouble();
            m=m+1;
            sum=sum+x;
            System.out.println("当前已输入第"+m+"个数，和为："+sum+"，平均数为"+(sum/m));

        }
        System.out.println(m+"个数的和为"+sum);//输出在循环里会造成输入之后直接出结果
        System.out.println(m+"个数的平均数为"+(sum/m));

        scanner.close();
    }
5.

public class Dome04 {

    public static void main(String[] args) {
        Scanner scanner = new Scanner(System.in);
        int i=0;
        float f=0.0f;
        System.out.println("请输入整数数据:");

        if (scanner.hasNextInt()){
            i=scanner.nextInt();
            System.out.println("输入的整数为： "+i);
        }
        else {
            System.out.println("输入的不是整数！");
        }
            System.out.println("请输入小数数据:");

            if (scanner.hasNextFloat()){
                f=scanner.nextFloat();
                System.out.println("输入的小数为： "+f);
            }
            else{
                System.out.println("输入的不是小数！");

            }
        scanner.close();
    }
6.

public class Demo06 {
    public static void main(String[] args) {
        Scanner scanner = new Scanner(System.in);
        while (scanner.hasNextDouble()){
            double x=scanner.nextDouble();
            System.out.println(x);
        }



        scanner.close();
    }
}