package collection;

public class TestCollection {
	
	public static void main(String[] args) {
		for (int i = 0; i < 100; i++) {
			int length = (int) (Math.random()*8+2);
			String str = randomString(length);
			int hashcode = hashcode(str);
			System.out.printf("%-11s的自定义hashcode是:%d%n",str,hashcode);			
		}
		
	}

	private static int hashcode(String str) {
		// TODO Auto-generated method stub
		if(0==str.length())
			return 0;
		
		int hashcode = 0;
		char[]cs= str.toCharArray();
		for (int i = 0; i < cs.length; i++) {
			hashcode +=cs[i];
		}
		hashcode*=23;
		//取绝对值
		hashcode = hashcode<0?0-hashcode:hashcode;
		//落在0-1999之间
		hashcode %=2000;
		
		return hashcode;
	}
	
	private static String randomString(int length) {
		String pool = "";
		for (short i = '0'; i <= '9'; i++) {
			pool += (char) i;
		}
		for (short i = 'a'; i <= 'z'; i++) {
			pool += (char) i;
		}
		for (short i = 'A'; i <= 'Z'; i++) {
			pool += (char) i;
		}
		char cs[] = new char[length];
		for (int i = 0; i < cs.length; i++) {
			int index = (int) (Math.random() * pool.length());
			cs[i] = pool.charAt(index);
		}
		String result = new String(cs);
		return result;
	}
	
}

package collection;

import java.util.LinkedList;

public class MyHashMap implements IHashMap {
	LinkedList<Entry>[] values = new LinkedList[2000];

	@Override
	public void put(String key, Object object) {
		// 拿到hashcode
		int hashcode = hashcode(key);

		// 找到对应的LinkedList
		LinkedList<Entry> list = values[hashcode];
		// 如果LinkedList是null，则创建一个LinkedList
		if (null == list) {
			list = new LinkedList<>();
			values[hashcode] = list;
		}

		// 判断该key是否已经有对应的键值对
		boolean found = false;
		for (Entry entry : list) {
			// 如果已经有了，则替换掉
			if (key.equals(entry.key)) {
				entry.value = object;
				found = true;
				break;
			}
		}

		// 如果没有已经存在的键值对，则创建新的键值对
		if (!found) {
			Entry entry = new Entry(key, object);
			list.add(entry);
		}

	}

	@Override
	public Object get(String key) {
		// 获取hashcode
		int hashcode = hashcode(key);
		// 找到hashcode对应的LinkedList
		LinkedList<Entry> list = values[hashcode];
		if (null == list)
			return null;

		Object result = null;

		// 挨个比较每个键值对的key，找到匹配的，返回其value
		for (Entry entry : list) {
			if (entry.key.equals(key)) {
				result = entry.value;
				break;
			}
		}

		return result;

	}

	private static int hashcode(String str) {
		// TODO Auto-generated method stub
		if (0 == str.length())
			return 0;

		int hashcode = 0;
		char[] cs = str.toCharArray();
		for (int i = 0; i < cs.length; i++) {
			hashcode += cs[i];
		}
		hashcode *= 23;
		// 取绝对值
		hashcode = hashcode < 0 ? 0 - hashcode : hashcode;
		// 落在0-1999之间
		hashcode %= 2000;

		return hashcode;
	}

	public static void main(String[] args) {
		 MyHashMap map =new MyHashMap();
		//
		// map.put("t", "坦克");
		// map.put("adc", "物理");
		// map.put("apc", "魔法");
		// map.put("t", "坦克2");
		//
		// System.out.println(map.get("adc"));
		//
		// System.out.println(map);
		
		 System.out.println(map.hashcode("name=hero-2387"));
		 System.out.println(map.hashcode("name=hero-5555"));

	}

	public String toString() {
		LinkedList<Entry> result = new LinkedList();

		for (LinkedList<Entry> linkedList : values) {
			if (null == linkedList)
				continue;
			result.addAll(linkedList);
		}
		return result.toString();
	}

}

package collection;
 
import java.util.ArrayList;
import java.util.List;

import charactor.Hero;
 
public class TestCollection {
    public static void main(String[] args) {
        List<Hero> hs =new ArrayList<>();
        System.out.println("初始化开始");
        for (int i = 0; i < 100000; i++) {
            Hero h = new Hero(   "hero-" + random());
            hs.add(h);
        }
        //名字作为key
        //名字相同的hero，放在一个List中，作为value
        MyHashMap heroMap =new MyHashMap();
        for (Hero h : hs) {
            List<Hero> list= (List<Hero>) heroMap.get( h.name);
            if(list==null){
                list = new ArrayList<>();
                heroMap.put(h.name, list);
            }
            list.add(h);
        }
         
        System.out.println("初始化结束");
        System.out.println("开始查找");
        findByIteration(hs);
        findByMap(heroMap);
         
    }
    private static List<Hero> findByMap(MyHashMap m) {
        long start =System.currentTimeMillis();
        List <Hero>result= (List<Hero>) m.get("hero-5555");
        long end =System.currentTimeMillis();
        System.out.printf("通过map查找，一共找到%d个英雄，耗时%d 毫秒%n",result.size(),end-start);
        return result;
    }
    private static List<Hero> findByIteration (List<Hero> hs) {
        long start =System.currentTimeMillis();
        List<Hero> result =new ArrayList<>();
        for (Hero h : hs) {
            if(h.name.equals("hero-5555")){
                result.add(h);
            }
        }
        long end =System.currentTimeMillis();
        System.out.printf("通过for查找，一共找到%d个英雄，耗时%d 毫秒%n", result.size(),end-start);
        return result;
    }
    public static int random(){
        return ((int)(Math.random()*9000)+1000);
    }
}