关于ArrayList练习的问题 - 黑马程序员技术交流社区

import java.util.*;
class Person
{
private String name;
private int age;
Person(String name,int age)
{
this.name=name;
this.age=age;
}
public boolean equals(Object obj)
{
if(!(obj instanceof Person))
return false;
Person p=(Person)obj;
return this.name.equals(p.name)&&this.age==p.age;
}
public String getName()
{
return name;
}
public int getAge()
{
return age;
}
}
class ArrayListTest2
{
public static void sop(Object obj)
{
System.out.println(obj);
}
public static void main(String[] args)
{
ArrayList al=new ArrayList();
al.add(new Person("lisi01",30));//al.add(Object obj); Object obj=new Person("lisi01",30);Person会被提升为Object类型。
al.add(new Person("lisi02",32));
al.add(new Person("lisi02",32));
al.add(new Person("lisi03",33));
al.add(new Person("lisi04",35));
al.add(new Person("lisi04",35));
al=singleElement(al);
Iterator it=al.iterator();
while(it.hasNext())
{
/*
Object obj=it.next();
Person p=(Person)obj;
*/
Person p=(Person)it.next();
sop(p.getName()+":::"+p.getAge());
}
}
public static ArrayList singleElement(ArrayList al)
{
//定义一个临时容器
ArrayList newAl=new ArrayList();
Iterator it= al.iterator();//遍历老集合
while(it.hasNext())
{
Object obj=it.next();//获取一个元素用obj记下来
if(!newAl.contains(obj))
newAl.add(obj);
}
return newAl;
}
}

复制代码