Double vs float-java[重复]

Question

public class Testing {

    public static void main(String[] args) {

         float     piF =  3.141592653589793f;   // value assigned has float precision
         double    piD =  3.141592653589793;   //  value assigned has double precision
         final double THRESHOLD = .0001; 
         if( piF == piD) 
            System.out.println( "piF and piD are equal" ); 
         else 
            System.out.println( "piF and piD are not equal" ); 
         if( Math.abs( piF - (float) piD ) < THRESHOLD ) 
            System.out.println( "piF and piD are considered equal" ); 
         else 
            System.out.println( "piF and piD are not equal" ); 

    }

}

结果：

piF and piD are not equal
piF and piD are considered equal

为什么piF和piD不相等呢？math.abs()实际上是什么使两者相同？

Answer 1

我在终端中运行这个命令，然后添加piF和piD值的print语句，结果如下：

piF and piD are not equal
piF and piD are considered equal
piF = 3.1415927
piD = 3.141592653589793

当你直接比较这两者时，它们是不相等的。但是当您将piD强制转换为浮点类型时，它将变为：

(float) piD = 3.1415927

当你不明白结果的时候，尝试在变量上使用print语句，这是学习这些东西的一个很好的方法！

    System.out.println("piF = " + piF);
    System.out.println("piD = " + piD);

    System.out.println("(float) piD = " + (float) piD);