为什么报scanner错误？？

[攻城狮AndLi]

package com.javabook.cho2;
import java.util.*;

public class Equation {
public static void main(String []args)
{
Scanner s=new Scanner(System.in);
System.out.println("请输入a：");
float a=s.nextFloat();
System.out.println("请输入b：");
float b=s.nextFloat();
System.out.println("请输入c：");
float c=s.nextFloat();
double delta=b*b-4*a*c;
if(delta>0)
{
double x1=(-b+Math.sqrt(delta))/(a*2);
double x2=(-b-Math.sqrt(delta))/(a*2);
System.out.println("方程的两个不同实根：");
System.out.println("x1="+x1);
System.out.println("x2="+x2);
}
else if(delta==0)
{
double x1=(-b)/(2*a);
double x2=x1;
System.out.println("x1="+x1);
System.out.println("x2="+x2);
}
else
{
System.out.println("无解！！");

}
}

}
错误提示：
java.lang.Error: Unresolved compilation problems:
Scanner cannot be resolved to a type
Scanner cannot be resolved to a type

at com.javabook.cho2.Equation.main(Equation.java:7)
Exception in thread "main"

[shiyiwan]

JDK版本是否在1.5以下？

[攻城狮AndLi]

是的

[shiyiwan]

1.5以下的jdk中还没有Scanner这个类

[攻城狮AndLi]

谢谢了！！