Double vs Float - Java

Question

那麼我有以下程序。這是我的老師給的樂趣。我對結果感到驚訝。

代碼：

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"); 

    } 

} 

結果：

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

那麼爲什麼PIF和PID不相等？而實際上Math.abs()這樣做是否使兩者相同？

Answer 1

我在終端跑了這一點，那麼添加PIF和PID值打印報表和這裏的結果：

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

當你做兩者之間的直接比較，他們是不相等的。但是，當你施放PID號浮點類型，就變成這樣：

(float) piD = 3.1415927 

嘗試使用打印語句上的變量，當你不理解的結果，這是瞭解這個東西，一個偉大的方式！

這裏是打印語句我加供大家參考：

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

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