1. 泛型的擦除
public void ta(List<Integer> b) {
System.out.println("b");
}
public void ta(List<String> c) {
System.out.println("c");
}
编译出错，因为在编译器看来都是List
2. 自动装箱和拆箱
import java.util.*;
class A {
}
class B extends A {
}
class C extends A {
}
public class Test {
/**
* @param args
*/
public static void main(String[] args) {
// TODO Auto-generated method stub
Integer a = 1;
Integer b = 2;
Integer c = 3;
Integer d = 3;
Integer e = 321;
Integer f = 321;
Character cc = 3;
Long g = 3L;
System.out.println(a == b);
System.out.println(e == f);
System.out.println(g.equals(a+b));
System.out.println(cc.equals(a + b));
System.out.println(c == (a + b));
System.out.println(c.equals(a + b));
System.out.println(g == (a+b));
System.out.println(a == 1);
System.out.println(g == 3);
}
}
output:
false
false
false
false
true
true
true
true
true
equals首先要判断传入的参数是否是同一类型的
==比较的是对象地址
但是当有算数运算时，比如+,就自动拆箱为基本类型
如果==比较的一方是基本类型，另一方也拆箱为基本类型