1 package test; 2  3 public class Square {   4     long width;   5     public Square(long l) {    6         width = l;   7     }   8     public static void main(String arg[]) {    9         Square a, b, c;  10         a = new Square(42L);   11         b = new Square(42L);   12         c = b;   13         long s = 42L;  14         System.out.println(a == b); // false15         //System.out.println(s == a); //Incompatible operand types long and Square16         System.out.println(b == c); // true17         System.out.println(a.equals(s)); // false18     } 19 }

 

在上面的例子中，a与b为Square的实例，为两个不同的对象；

s为基本类型，与对象进行比较时会报错，报错类型：Incompatible operand types long and Square