java新手笔记31 集合实现类

时间：2023-03-09 20:22:33
java新手笔记31 集合实现类

Person类：

package com.yfs.javase;

import java.util.Date;

public class Person implements Comparable {

	private String name;

	private int age;

	private char sex;

	public static Date date = new Date();

	@Override

	public int hashCode() {

		final int prime = 31;

		int result = 1;

		result = prime * result + age;

		result = prime * result + ((name == null) ? 0 : name.hashCode());

		result = prime * result + sex;

		return result;

	}

	@Override

	public boolean equals(Object obj) {

		if (this == obj)

			return true;

		if (obj == null)

			return false;

		if (getClass() != obj.getClass())

			return false;

		Person other = (Person) obj;

		if (age != other.age)

			return false;

		if (name == null) {

			if (other.name != null)

				return false;

		} else if (!name.equals(other.name))

			return false;

		if (sex != other.sex)

			return false;

		return true;

	}

	public Person() {

	}

	public Person (String n) {

		this.name = n;

	}

	public String getName() {

		return name;

	}

	public void setName(String name) {

		this.name = name;

	}

	public int getAge() {

		return age;

	}

	public void setAge(int age) {

		this.age = age;

	}

	public char getSex() {

		return sex;

	}

	public void setSex(char sex) {

		this.sex = sex;

	}

	@Override

	public String toString() {

		return "Person [name=" + name + ", age=" + age + ", sex=" + sex + "]";

	}

	public Person(String name, int age, char sex) {

		super();

		this.name = name;

		this.age = age;

		this.sex = sex;

	}

	@Override

	public int compareTo(Object o) {

		Person p = (Person)o;

		return p.age - age;

	}

}

1.set

package com.yfs.javase;

import java.util.ArrayList;

import java.util.Collection;

import java.util.HashSet;

import java.util.Iterator;

import java.util.LinkedHashSet;

import java.util.LinkedList;

import java.util.List;

import java.util.Set;

import java.util.SortedSet;

import java.util.TreeSet;

public class Demo1 {

	/**

	 * Set

	 */

	public static void main(String[] args) {

//		LinkedHashSet lSet = null;//增加 删除

//		HashSet hSet = null;//查找

//		TreeSet tSet = null;//排序

//		useLinkedSet();

		//useTreeSet();

		useArrayList();

	}

	public static void useArrayList() {

		ArrayList list = new ArrayList();//必须覆盖equals方法

		Person p = new Person("张三",20,'男');

		list.add(p);

		list.add(new Person("李四",23,'女'));

		list.add(new Person("王五",22,'男'));

		list.add(new Person("王Z",21,'女'));

		list.add(p);

		System.out.println("是否有张三：" + list.contains(p));//指向同一对象

		System.out.println("是否有张三：" + list.contains(new Person("张三",20,'男')));

		System.out.println("元素：" + list);

	}

	public static void useTreeSet() {

		TreeSet tSet = new TreeSet();

		tSet.add("fff");

		tSet.add("ccc");

		tSet.add("aaa");

		tSet.add("ddd");

		tSet.add("aaa");

		System.out.println("元素个数： " + tSet.size());

		System.out.println("元素： " + tSet);

	}

	public static void useLinkedSet() {

		LinkedHashSet lSet = new LinkedHashSet();

		lSet.add("fff");

		lSet.add("ccc");

		lSet.add("aaa");

		lSet.add("ddd");

		lSet.add("aaa");

		System.out.println("元素个数： " + lSet.size());

		System.out.println("元素： " + lSet);

	}

}

2.Mycompare类

package com.yfs.javase;

import java.util.Comparator;

//外部比较器

public class Mycompare implements Comparator {

	@Override

	public int compare(Object o1, Object o2) {

		Person p1 = (Person)o1;

		Person p2 = (Person)o2;

		return p1.getAge() - p2.getAge();//使用年龄排序

	}

}

使用比较器:

package com.yema.javase;

import java.util.ArrayList;

import java.util.Collection;

import java.util.HashSet;

import java.util.Iterator;

import java.util.LinkedHashSet;

import java.util.LinkedList;

import java.util.List;

import java.util.Set;

import java.util.SortedSet;

import java.util.TreeSet;

public class Demo2 {

	/**

	 * Set

	 */

	public static void main(String[] args) {

		//useLinkedSet();

		useTreeSet();

//		useArrayList();

	}

	public static void useArrayList() {

		ArrayList list = new ArrayList();//必须覆盖equals方法

		Person p = new Person("张三",20,'男');

		list.add(p);

		list.add(new Person("李四",23,'女'));

		list.add(new Person("王五",22,'男'));

		list.add(new Person("王Z",21,'女'));

		list.add(p);

		System.out.println("是否有张三：" + list.contains(p));//指向同一对象

		System.out.println("是否有张三：" + list.contains(new Person("张三",20,'男')));

		System.out.println("元素：" + list);

	}

	public static void useTreeSet() {

//		Mycompare com = new Mycompare();//使用比较器

//		TreeSet  tSet = new TreeSet(com);//必须覆盖hashcode equals方法

		TreeSet  tSet = new TreeSet();//必须覆盖hashcode equals方法

		Person p = new Person("张三",20,'男');

		tSet.add(p);

		tSet.add(new Person("李四",23,'女'));

		tSet.add(new Person("王五",22,'男'));

		tSet.add(new Person("王Z",21,'女'));

		tSet.add(p);

		System.out.println("是否有张三：" + tSet.contains(p));//指向同一对象

		System.out.println("是否有张三：" + tSet.contains(new Person("张三",20,'男')));

		System.out.println("元素：" + tSet);

	}

	public static void useLinkedSet() {

		LinkedHashSet  lSet = new LinkedHashSet();//必须覆盖hashcode equals方法

		Person p = new Person("张三",20,'男');

		lSet.add(p);

		lSet.add(new Person("李四",23,'女'));

		lSet.add(new Person("王五",22,'男'));

		lSet.add(new Person("王Z",21,'女'));

		lSet.add(p);

		System.out.println("是否有张三：" + lSet.contains(p));//指向同一对象

		System.out.println("是否有张三：" + lSet.contains(new Person("张三",20,'男')));

		System.out.println("元素：" + lSet);

	}

}

3.泛型

package com.yfs.javase;

import java.util.ArrayList;

import java.util.Collection;

import java.util.HashSet;

import java.util.Iterator;

import java.util.Random;

public class Demo3 {

	/**

	 * 泛型

	 */

	public static void main(String[] args) {

		// useArrayList();

		useCollection();

	}

	private static void useCollection() {

		// 指定集合放入对象类型

		Collection<Person> col = new HashSet<Person>();

		col.add(new Person("张三", 20, '男'));

		col.add(new Person("李四", 23, '女'));

		col.add(new Person("王五", 22, '男'));

		col.add(new Person("王Z", 21, '女'));

		// list.add(new Random()); 其他类型对象不能放入

		System.out.println("元素：" + col);

		// Person p = (Person)list.get(4);

		// Object obj = list.get(4);

		// 取值不考虑类型 迭代器泛型

		Iterator<Person> it = col.iterator();

		while (it.hasNext()) {

			Person p = it.next();

			System.out.println(p);

		}

	}

	public static void useArrayList() {

		// 指定集合放入对象类型

		ArrayList<Person> list = new ArrayList<Person>();

		list.add(new Person("张三", 20, '男'));

		list.add(new Person("李四", 23, '女'));

		list.add(new Person("王五", 22, '男'));

		list.add(new Person("王Z", 21, '女'));

		// list.add(new Random()); 其他类型对象不能放入

		System.out.println("元素：" + list);

		// Person p = (Person)list.get(4);

		// Object obj = list.get(4);

		Person p = list.get(2);// 取值不考虑类型

	}

}

4.HashMap

package com.yfs.javase;

import java.util.HashMap;

import java.util.Map;

import java.util.Random;

public class MapDemo1 {

	/**

	 * @param args

	 */

	public static void main(String[] args) {

		Map map = new HashMap();

		map.put(1, new Person());//put添加对象key value

		map.put(2, new Random());

		map.put("zhangsan", "1388888888");

		map.put("lisi", "139999999");

		map.put("zhangsan", "1300000000");

		System.out.println("元素个数 ： " + map.size());

		System.out.println("元素： " + map);

		System.out.println(map.get(1));

		System.out.println(map.get("lisi"));

		System.out.println("是否有zhangsan key ：" + map.containsKey("zhangsan"));

		System.out.println("是否有139999999号码：" + map.containsValue("139999999"));

	}

}

5.Map（Iterator)实体、key的集合

package com.yfs.javase;

import java.util.Collection;

import java.util.Date;

import java.util.HashMap;

import java.util.Iterator;

import java.util.Map;

import java.util.Set;

public class MapDemo2 {

	/**

	 * @param args

	 */

	public static void main(String[] args) {

		//useMap();

		//useMapEntry();

		//Date d = Person.date;

		useKey();

	}

	public static void useMapEntry() {

		Map<String,String> map = new HashMap<String,String>();

		map.put("zhangsan", "1388888888");

		map.put("lisi", "139999999");

		map.put("zhang", "1300000000");

		map.put("wangwu", "1311111111");

		map.put("Tom", "1583333333333");

		map.put("Jack", "133333333333");

		Set<Map.Entry<String, String>> set = map.entrySet();//===================不同

		for(Iterator<Map.Entry<String, String>> it = set.iterator(); it.hasNext();){

			 Map.Entry<String, String> entry = it.next();

			 String key = entry.getKey();

			 String value= entry.getValue();

			 System.out.println(key + " === > " +  value);

		}

	}

	public static void useKey() {

		Map<String,String> map = new HashMap<String,String>();

		map.put("zhangsan", "1388888888");

		map.put("lisi", "139999999");

		map.put("zhang", "1300000000");

		map.put("wangwu", "1311111111");

		map.put("Tom", "1583333333333");

		map.put("Jack", "133333333333");

		System.out.println("元素个数 ： " + map.size());

		System.out.println("元素： " + map);

		//所有key 集合

		System.out.println("==========key + value 集合==========");

		Set set = map.keySet();//========================================不同

		for(Iterator<String> it = set.iterator(); it.hasNext();){

			String key = it.next();//keyjihe

			System.out.print(key + " +++ ");

			String value = map.get(key);// mapjihe

			System.out.print(value + "\n");

		}

	}

}

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