Java集合框架详解

Collection接口用于单个元素装入，Map接口用于成对元素装入；

Set接口和List接口继承于Collection，Set存储无序且不可重复的元素，List存储有序且可重复的元素；

接口定义了标准，类具体实现对应标准。

Collection的子类用于存放的元素都是对象类型的（Object及其子类）。如果对象是自定义类的对象，则需要重写equal方法；

当需要用hash做索引时（如HashSet比较两个自定义对象，或Map中），也需要重写hashcode方法。

import java.util.*;

public class BasicContainer {

public static void main(String[] args) {

Collection c = new ArrayList();

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","l1")));

System.out.println(c);

}

}

class Name implements Comparable {

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 compareTo(Object o) {

Name n = (Name)o;

int lastCmp =

lastName.compareTo(n.lastName);

return

(lastCmp!=0 ? lastCmp :

firstName.compareTo(n.firstName));

}

}

父类引用（接口引用）指向子类对象应用此处应用较广：

Collection c = new ArrayList();