public class C3 {     //default 8     public byte b = 2 ; //1         public short s = 2 ; //2     public char c = '2' ; //2         public int i = 2 ; //4     public float f = 2.0f ; //4         public double d = 2.0 ; //8     public long l = 2l ; //8         public String str = "1" ; //4     //total 41 }

//上面忘了测试boolean，测试工具为“visualvm”

public class C4 extends C3 {     //C3类型部分 大小 41     public int i = 23 ; //4     public Object obj ; //4     public Object obj2 = null ; //4     public Object obj3 = new Object(); //4     public Object obj4 = new C3(); //4     public C3 c3 = new C3(); //4     //总占用 65     //这里的占用内存多少，并没有计算对象类型变量实例（如new Object()、new C3()）所占内存     //如：在这个类的实例中生成了两个“C3”类型对象共用去82byte内存（也没计算内部对象所占内存） }