Java集合及其排序

目录

 

1.集合 = Collection+Map

2.实现集合排序

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1.集合 = Collection+Map

（Java 集合框架主要包括两种类型的容器，一种是集合（Collection），存储一个元素集合，另一种是图（Map），存储键/值对映射。）

Collection = Set + List + Queue
    Set = HashSet (乱序）
          + LinkedHashSet （按插入有序）
          + TreeSet
    List = ArrayList（数组实现）
           + LinkedList（链表实现

Map = HashMap(散列图，null可以为key）
        + LinkedHashMap（链式散列图，按插入顺序或者访问顺序排序，双链表）
        + TreeMap （树形图）

2.实现集合排序

   （1）实现Comparable接口的compareTo方法
   （2）实现Comparator接口的compare方法

import java.util.*;


/**
 * java.lang.Comparable的compareTo方法是把排序逻辑写在类里边，自然排序，且 e1.compareTo(e2) == 0 的结果要和 e1.equals(e2)一致
 * java.util.Comparator的compare方法是把排序逻辑写在类外边，方便定制化。
 *
 */



public class CollectionTest {

	public static void main(String[] args) {
		Collection c;
		LinkedList llist;
		ArrayList alist;
//		Collections.sort();
		
		LinkedList list1;
		ArrayList list2;
		
		String ss;
		StringBuffer s1;
		StringBuilder s2;
		
		
		ArrayList list = new ArrayList();
		list.add( new Student("s60", 60));
		list.add( new Student("s40", 40));
		list.add( new Student("s80", 80));
		list.add( new Student("s50", 50));
		
		Iterator it = list.iterator();
		while(it.hasNext()) {
			System.out.println(((Student)it.next()).getName());
		}
		
		Collections.sort(list,new SortByScore());
		

		for (Student s: list) {
			System.out.println(s.getName());
		}
		
		System.out.println("------Student2 start------");
		ArrayList listStudent2 = new ArrayList();
		listStudent2.add( new Student2("s60", 60));
		listStudent2.add( new Student2("s40", 40));
		listStudent2.add( new Student2("s80", 80));
		listStudent2.add( new Student2("s50", 50));
		
		Iterator it2 = listStudent2.iterator();
		while(it2.hasNext()) {
			System.out.println(((Student2)it2.next()).getName());
		}
		
		Collections.sort(listStudent2);
		
		for (Student2 s: listStudent2) {
			System.out.println(s.getName());
		}
		
		System.out.println("------Student2 end------");

		
		Map map = new HashMap();
		map.put("s60", 60);
		map.put("s40", 40);
		map.put("s80", 80);
		map.put("s50", 50);
		
		Iterator mapit = map.entrySet().iterator();
		while (mapit.hasNext()) {
			Map.Entry entry = (Map.Entry)mapit.next();
			System.out.println(entry.getKey());
			System.out.println(entry.getValue());
		}
		
	}
	
	
    static class Student  {
		
		public String getName() {
			return name;
		}

		public void setName(String name) {
			this.name = name;
		}

		public int getScore() {
			return score;
		}

		public void setScore(int score) {
			this.score = score;
		}

		String name;
		int score;
		
		public Student(String name, int score) {
			this.name = name;
			this.score = score;
		}
		
	}
	
	static class SortByScore implements Comparator {
		public int compare(Student s1, Student s2) {
			if (s1.score > s2.score) {
				return 1;
			} else if (s1.score < s2.score) {
				return -1;
			} else {
				return 0;
			}
		}
	}
	
	static class Student2 implements Comparable{
		public String getName() {
			return name;
		}

		public void setName(String name) {
			this.name = name;
		}

		public int getScore() {
			return score;
		}

		public void setScore(int score) {
			this.score = score;
		}

		String name;
		int score;
		
		public Student2(String name, int score) {
			this.name = name;
			this.score = score;
		}

//	s

		public int compareTo(Object o) {
			Student2 s2 = (Student2) o;
			if (this.score > s2.score) {
				return 1;
			} else if (this.score < s2.score) {
				return -1;
			} else {
				return 0;
			}
		}
	}
}