Java（18）Map

package Test.map;

import org.junit.jupiter.api.Test;

import java.util.Map;
import java.util.concurrent.ConcurrentHashMap;


public class ConcurrentHashMapTest {
    @Test
    public void test() {
        Map map = new ConcurrentHashMap<>();
        map.put("xm", 18);
        System.out.println(map.get("xm"));
    }
//18    
}

package Test.map;

import org.junit.jupiter.api.Test;

import java.util.*;
import java.util.concurrent.ThreadLocalRandom;


public class HashMapTest {
    @Test
    public void test01() {
        Map map = new HashMap<>();
        map.put("xm", 95);
        map.put("x", 90);
        System.out.println(map.get("xm"));
        System.out.println(map.get("x"));
    }

    @Test
    public void test02() {
        Map map = new HashMap<>();
        map.put("xm", 95);
        map.put("x", 90);
        map.put("xm", 66);
        System.out.println("size >>> " + map.size());
        System.out.println("xm >>> " + map.get("xm"));
        System.out.println("x >>> " + map.get("x"));
    }

    @Test
    public void test03() {
        Map map = new HashMap<>();
        map.put("xm", 95);
        map.put("x", 90);
        System.out.println("size >>> " + map.size());
        System.out.println("xm >>> " + map.get("xm"));
        System.out.println("x >>> " + map.get("x"));
        map.remove("x");
        System.out.println("size >>> " + map.size());
        System.out.println("xm >>> " + map.get("xm"));
        System.out.println("x >>> " + map.get("x"));
    }

    @Test
    public void test04() {
        Map map = new HashMap<>();
        map.put("xm", 95);
        map.put("x", 90);
        System.out.println("size >>> " + map.size());
        System.out.println("xm >>> " + map.get("xm"));
        System.out.println("x >>> " + map.getOrDefault("x", 0));
        map.remove("x");
        System.out.println("size >>> " + map.size());
        System.out.println("xm >>> " + map.get("xm"));
        System.out.println("x >>> " + map.getOrDefault("x", 0));
    }

    @Test
    public void test05() {
        Map map = new HashMap<>();
        for (int i = 0; i < 10; i++) {
            map.put("xm" + (i + 1), ThreadLocalRandom.current().nextInt(100));
        }
        // 获取集合中所有的key
        Set keySet = map.keySet();
        Iterator it = keySet.iterator();
        while (it.hasNext()) {
            String key = it.next();
            System.out.println("key >>> " + key + "tvalue >>> " + map.get(key));
        }
    }

    @Test
    public void test06() {
        Map map = new HashMap<>();
        for (int i = 0; i < 10; i++) {
            map.put("xm" + (i + 1), ThreadLocalRandom.current().nextInt(100));
        }
        Set> entrySet = map.entrySet();
        Iterator> it = entrySet.iterator();
        while (it.hasNext()){
            Map.Entry entry = it.next();
            System.out.println("key >>> " + entry.getKey() + "tvalue >>> " + entry.getValue());
        }
    }

    @Test
    public void test07() {
        Map map = new HashMap<>();
        for (int i = 0; i < 10; i++) {
            map.put("xm" + (i + 1), ThreadLocalRandom.current().nextInt(100));
        }
        Collection values = map.values();
        Iterator it = values.iterator();
        while (it.hasNext()){
            Integer value = it.next();
            System.out.println(value);
        }
    }

    @Test
    public void test08() {
        Map map = new HashMap<>();
        for (int i = 0; i < 10; i++) {
            map.put("xm" + (i + 1), ThreadLocalRandom.current().nextInt(100));
        }
        // 判断map中是否存在key
        System.out.println(map.containsKey("xm"));
        System.out.println(map.containsKey("xm3"));
    }

}

package Test.map;

import org.junit.jupiter.api.Test;

import java.util.Hashtable;
import java.util.Map;


public class HashtableTest {
    @Test
    public void test() {
        Map map = new Hashtable<>();
        map.put("xm", 95);
        System.out.println(map.get("xm"));
    }
//95    
}

package Test.map;

import org.junit.jupiter.api.Test;

import java.util.Iterator;
import java.util.LinkedHashMap;
import java.util.Map;
import java.util.Set;
import java.util.concurrent.ThreadLocalRandom;


public class LinkedHashMapTest {

    @Test
    public void test05() {
        Map map = new LinkedHashMap<>();
        for (int i = 0; i < 10; i++) {
            map.put("xm" + (i + 1), ThreadLocalRandom.current().nextInt(100));
        }
        // 获取集合中所有的key
        Set keySet = map.keySet();
        Iterator it = keySet.iterator();
        while (it.hasNext()) {
            String key = it.next();
            System.out.println("key >>> " + key + "tvalue >>> " + map.get(key));
        }
    }

    @Test
    public void test06() {
        Map map = new LinkedHashMap<>();
        for (int i = 0; i < 10; i++) {
            map.put("xm" + (i + 1), ThreadLocalRandom.current().nextInt(100));
        }
        Set> entrySet = map.entrySet();
        Iterator> it = entrySet.iterator();
        while (it.hasNext()) {
            Map.Entry entry = it.next();
            System.out.println("key >>> " + entry.getKey() + "tvalue >>> " + entry.getValue());
        }
    }

}