Collection接口

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1.容器类对象在调用remove，contains等方法时需要比较对象是否相等，这会涉及到对象类型的equals方法和hashCode方法；对于自定义的类型，需要重写equals方法和hashCode方法以实现自定义的对象相等原则。

2.注意：相等的对象应该具有相等的hash codes。

增加Name类的equals和hashCode方法如下：

public boolean equals(Object obj){if(obj instanceof Name){Name name=(Name) obj;return (Firstname.equals(name.Firstname))&&(Lastname.equals(name.Lastname));}return super.equals(obj);}public int hashcCode(){return Firstname.hashCode();}

Collection 方法举例：

import java.util.*;public class Basiccontainer {public static void main(String[] args){Collection c=new HashSet();    c.add("hello");    c.add(new Name("f1","l1"));    c.add(new Integer(100));    c.remove("hello");    c.remove(new Integer(100));    System.out.println(c.remove(new Name("f1","ll1")));    System.out.println(c);}}class Name{private String Firstname,Lastname;public Name(String Firstname,String Lastname){    this.Firstname=Firstname;this.Lastname=Lastname;}public String getFirstname(){return Firstname;}public String getLastname(){return Lastname;}public String tostring(){return Firstname+" "+Lastname;}public boolean equals(Object obj){if(obj instanceof Name){Name name=(Name) obj;return (Firstname.equals(name.Firstname))&&(Lastname.equals(name.Lastname));}return super.equals(obj);}public int hashcCode(){return Firstname.hashCode();}}

运行结果：

false[Name@5dcba031]

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