Scanner

public class Demo1 {
public static void main(String[] args) {
Scanner scanner = new Scanner(System.in);

System.out.println("请输入内容:");

//判断用户有没有输入字符串
if (scanner.hasNextLine()){ //hasNext() 会消除空格
String s = scanner.nextLine(); //scanner.next 会消除空格
System.out.println("内容为："+s);
}

//凡是属于IO流的类如果不关闭会一直占用资源，所有要养好习惯
scanner.close();
}
}

 

public class Demo2 {
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：");

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

System.out.println("请输入小数：");

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

scanner.close();
}
}
}

 

public class Demo3 {
public static void main(String[] args) {
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
while (scanner.hasNextDouble()){
double x = scanner.nextDouble();
m++;
sum = sum + x;
System.out.println("你输入了第"+m+"个数据，结果为"+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();
}
}