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最新推荐文章于 2025-09-29 15:34:38 发布

原创最新推荐文章于 2025-09-29 15:34:38 发布 · 341 阅读

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由于内容为空，暂无法提供包含关键信息的摘要。

import java.util.Enumeration;
import java.util.HashMap;
import java.util.Iterator;
import java.util.Map;
import java.util.Map.Entry;

public class HashMapTest {

	public static void main(String[] args) {
		HashMap<Integer,String> hm =new  HashMap<Integer,String>();
		hm.put(1, null); 
		hm.put(null, "abc");  
		hm.put(1000, "aaa");
		hm.put(2, "bbb");
		hm.put(30000, "ccc");
		System.out.println(hm.containsValue("aaa"));
		System.out.println(hm.containsKey(30000));
		System.out.println(hm.get(30000));
		
		hm.put(30000, "ddd");  //更新覆盖ccc
		System.out.println(hm.get(30000));
		
		hm.remove(2);
		System.out.println("size: " + hm.size());
		
		hm.clear();
		System.out.println("size: " + hm.size());
		
		
		HashMap<Integer,String> hm2 =new  HashMap<Integer,String>();
		for(int i=0;i<100000;i++)
		{
			hm2.put(i, "aaa");
		}
		traverseByEntry(hm2);
		traverseByKeySet(hm2);		
	}
	
	public static void traverseByEntry(HashMap<Integer,String> ht)
	{
		long startTime = System.nanoTime();
		System.out.println("============Entry迭代器遍历==============");
		Integer key;
		String value;
		Iterator<Entry<Integer, String>> iter = ht.entrySet().iterator();
		while(iter.hasNext()) {
		    Map.Entry<Integer, String> entry = iter.next();
		    // 获取key
		    key = entry.getKey();
		    // 获取value
		    value = entry.getValue();
		    //System.out.println("Key:" + key + ", Value:" + value);
		}
		long endTime = System.nanoTime();
	    long duration = endTime - startTime;
	    System.out.println(duration + "纳秒");
	}
	
	
	public static void traverseByKeySet(HashMap<Integer,String> ht)
	{
		long startTime = System.nanoTime();
		System.out.println("============KeySet迭代器遍历=============="); 
		Integer key;
		String value;
		Iterator<Integer> iter = ht.keySet().iterator();
		while(iter.hasNext()) {
		    key = iter.next();		    
		    // 获取value
		    value = ht.get(key);
		    //System.out.println("Key:" + key + ", Value:" + value);
		}
		long endTime = System.nanoTime();
	    long duration = endTime - startTime;
	    System.out.println(duration + "纳秒");
	}
}

import java.util.Enumeration;
import java.util.Hashtable;
import java.util.Iterator;
import java.util.Map;
import java.util.Map.Entry;

public class HashtableTest {

	public static void main(String[] args) {
		Hashtable<Integer,String> ht =new  Hashtable<Integer,String>();
		//ht.put(1, null); 编译不报错  运行报错
		//ht.put(null,1);  编译报错
		ht.put(1000, "aaa");
		ht.put(2, "bbb");
		ht.put(30000, "ccc");
		System.out.println(ht.contains("aaa"));
		System.out.println(ht.containsValue("aaa"));
		System.out.println(ht.containsKey(30000));
		System.out.println(ht.get(30000));
		
		ht.put(30000, "ddd");  //更新覆盖ccc
		System.out.println(ht.get(30000));
		
		ht.remove(2);
		System.out.println("size: " + ht.size());
		
		ht.clear();
		System.out.println("size: " + ht.size());
		
		
		Hashtable<Integer,String> ht2 =new  Hashtable<Integer,String>();
		for(int i=0;i<100000;i++)
		{
			ht2.put(i, "aaa");
		}
		traverseByEntry(ht2);
		traverseByKeySet(ht2);
		traverseByKeyEnumeration(ht2);		
	}
	
	public static void traverseByEntry(Hashtable<Integer,String> ht)
	{
		long startTime = System.nanoTime();
		System.out.println("============Entry迭代器遍历==============");
		Integer key;
		String value;
		Iterator<Entry<Integer, String>> iter = ht.entrySet().iterator();
		while(iter.hasNext()) {
		    Map.Entry<Integer, String> entry = iter.next();
		    // 获取key
		    key = entry.getKey();
		    // 获取value
		    value = entry.getValue();
		    //System.out.println("Key:" + key + ", Value:" + value);
		}
		long endTime = System.nanoTime();
	    long duration = endTime - startTime;
	    System.out.println(duration + "纳秒");
	}
	
	
	public static void traverseByKeySet(Hashtable<Integer,String> ht)
	{
		long startTime = System.nanoTime();
		System.out.println("============KeySet迭代器遍历=============="); 
		Integer key;
		String value;
		Iterator<Integer> iter = ht.keySet().iterator();
		while(iter.hasNext()) {
		    key = iter.next();		    
		    // 获取value
		    value = ht.get(key);
		    //System.out.println("Key:" + key + ", Value:" + value);
		}
		long endTime = System.nanoTime();
	    long duration = endTime - startTime;
	    System.out.println(duration + "纳秒");
	}
	
	
	public static void traverseByKeyEnumeration(Hashtable<Integer,String> ht)
	{
		long startTime = System.nanoTime();
		System.out.println("============KeyEnumeration迭代器遍历=============="); 
		Integer key;
		String value;
		Enumeration<Integer> keys = ht.keys();
		while(keys.hasMoreElements()) {
		    key = keys.nextElement();   
		    // 获取value
		    value = ht.get(key);
		    //System.out.println("Key:" + key + ", Value:" + value);
		}
		long endTime = System.nanoTime();
	    long duration = endTime - startTime;
	    System.out.println(duration + "纳秒");
	}
}

import java.util.HashMap;
import java.util.Hashtable;
import java.util.Iterator;
import java.util.Map;
import java.util.Map.Entry;

public class MapCompareTest {

	public static void main(String[] args) {
		int n = 1000000;
		System.out.println("============HashMap=============");
		HashMap<Integer,String> hm =new  HashMap<Integer,String>();
		for(int i=0;i<n;i++) {
			hm.put(i, "aaa");
		}
		traverseByEntry(hm);
		traverseByKeySet(hm);
		
		System.out.println("============Hashtable=============");
		Hashtable<Integer,String> ht2 =new  Hashtable<Integer,String>();
		for(int i=0;i<n;i++) {
			ht2.put(i, "aaa");
		}
		traverseByEntry(ht2);
		traverseByKeySet(ht2);
	}
	
	public static void traverseByEntry(Map<Integer,String> ht)
	{
		long startTime = System.nanoTime();
		System.out.println("============Entry迭代器遍历==============");
		Integer key;
		String value;
		Iterator<Entry<Integer, String>> iter = ht.entrySet().iterator();
		while(iter.hasNext()) {
		    Map.Entry<Integer, String> entry = iter.next();
		    // 获取key
		    key = entry.getKey();
		    // 获取value
		    value = entry.getValue();
		    //System.out.println("Key:" + key + ", Value:" + value);
		}
		long endTime = System.nanoTime();
	    long duration = endTime - startTime;
	    System.out.println(duration + "纳秒");
	}
	
	
	public static void traverseByKeySet(Map<Integer,String> ht)
	{
		long startTime = System.nanoTime();
		System.out.println("============KeySet迭代器遍历=============="); 
		Integer key;
		String value;
		Iterator<Integer> iter = ht.keySet().iterator();
		while(iter.hasNext()) {
		    key = iter.next();		    
		    // 获取value
		    value = ht.get(key);
		    //System.out.println("Key:" + key + ", Value:" + value);
		}
		long endTime = System.nanoTime();
	    long duration = endTime - startTime;
	    System.out.println(duration + "纳秒");
	}
}

import java.util.LinkedHashMap;
import java.util.Iterator;
import java.util.Map;
import java.util.Map.Entry;

public class LinkedHashMapTest {

	public static void main(String[] args) {
		LinkedHashMap<Integer,String> hm =new  LinkedHashMap<Integer,String>();
		hm.put(1, null); 
		hm.put(null, "abc");  
		hm.put(1000, "aaa");
		hm.put(2, "bbb");
		hm.put(30000, "ccc");
		System.out.println(hm.containsValue("aaa"));
		System.out.println(hm.containsKey(30000));
		System.out.println(hm.get(30000));
		
		hm.put(30000, "ddd");  //更新覆盖ccc
		System.out.println(hm.get(30000));
		
		hm.remove(2);
		System.out.println("size: " + hm.size());
		
		//hm.clear();
		//System.out.println("size: " + hm.size());
		
		System.out.println("遍历开始==================");
		
		Integer key;
		String value;
		Iterator<Entry<Integer, String>> iter = hm.entrySet().iterator();
		while(iter.hasNext()) {
		    Map.Entry<Integer, String> entry = iter.next();
		    // 获取key
		    key = entry.getKey();
		    // 获取value
		    value = entry.getValue();
		    System.out.println("Key:" + key + ", Value:" + value);
		}
		System.out.println("遍历结束==================");		
		
		LinkedHashMap<Integer,String> hm2 =new  LinkedHashMap<Integer,String>();
		for(int i=0;i<100000;i++)
		{
			hm2.put(i, "aaa");
		}
		traverseByEntry(hm2);
		traverseByKeySet(hm2);		
	}
	
	public static void traverseByEntry(LinkedHashMap<Integer,String> ht)
	{
		long startTime = System.nanoTime();
		System.out.println("============Entry迭代器遍历==============");
		Integer key;
		String value;
		Iterator<Entry<Integer, String>> iter = ht.entrySet().iterator();
		while(iter.hasNext()) {
		    Map.Entry<Integer, String> entry = iter.next();
		    // 获取key
		    key = entry.getKey();
		    // 获取value
		    value = entry.getValue();
		    //System.out.println("Key:" + key + ", Value:" + value);
		}
		long endTime = System.nanoTime();
	    long duration = endTime - startTime;
	    System.out.println(duration + "纳秒");
	}
	
	
	public static void traverseByKeySet(LinkedHashMap<Integer,String> ht)
	{
		long startTime = System.nanoTime();
		System.out.println("============KeySet迭代器遍历=============="); 
		Integer key;
		String value;
		Iterator<Integer> iter = ht.keySet().iterator();
		while(iter.hasNext()) {
		    key = iter.next();		    
		    // 获取value
		    value = ht.get(key);
		    //System.out.println("Key:" + key + ", Value:" + value);
		}
		long endTime = System.nanoTime();
	    long duration = endTime - startTime;
	    System.out.println(duration + "纳秒");
	}
}

import java.io.BufferedInputStream;
import java.io.File;
import java.io.FileInputStream;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;
import java.util.Enumeration;
import java.util.Properties;

//关于Properties类常用的操作
public class PropertiesTest {
    //根据Key读取Value
    public static String GetValueByKey(String filePath, String key) {
        Properties pps = new Properties();
        try {
            InputStream in = new BufferedInputStream (new FileInputStream(filePath));  
            pps.load(in); //所有的K-V对都加载了
            String value = pps.getProperty(key);
            //System.out.println(key + " = " + value);
            return value;
            
        }catch (IOException e) {
            e.printStackTrace();
            return null;
        }
    }
    
    //读取Properties的全部信息
    public static void GetAllProperties(String filePath) throws IOException {
        Properties pps = new Properties();
        InputStream in = new BufferedInputStream(new FileInputStream(filePath));
        pps.load(in); //所有的K-V对都加载了
        Enumeration en = pps.propertyNames(); //得到配置文件的名字
        
        while(en.hasMoreElements()) {
            String strKey = (String) en.nextElement();
            String strValue = pps.getProperty(strKey);
            //System.out.println(strKey + "=" + strValue);
        }
        
    }
    
    //写入Properties信息
    public static void WriteProperties (String filePath, String pKey, String pValue) throws IOException {
        File file = new File(filePath);
    	if(!file.exists())
    	{
    		file.createNewFile();
    	}
    	Properties pps = new Properties();
        
        InputStream in = new FileInputStream(filePath);
        //从输入流中读取属性列表（键和元素对） 
        pps.load(in);
        //调用 Hashtable 的方法 put。使用 getProperty 方法提供并行性。  
        //强制要求为属性的键和值使用字符串。返回值是 Hashtable 调用 put 的结果。
        OutputStream out = new FileOutputStream(filePath);
        pps.setProperty(pKey, pValue);
        //以适合使用 load 方法加载到 Properties 表中的格式，  
        //将此 Properties 表中的属性列表（键和元素对）写入输出流  
        pps.store(out, "Update " + pKey + " name");
        out.close();
    }
    
    public static void main(String [] args) throws IOException{
    	System.out.println("写入Test.properties================");
        WriteProperties("Test.properties","name", "12345");
        
        System.out.println("加载Test.properties================");
        GetAllProperties("Test.properties");
        
        System.out.println("从Test.properties加载================");
        String value = GetValueByKey("Test.properties", "name");
        System.out.println("name is " + value);
    }
}

import java.util.TreeMap;
import java.util.Iterator;
import java.util.Map;
import java.util.Map.Entry;

public class TreeMapTest {

	public static void main(String[] args) {
		TreeMap<Integer,String> hm =new  TreeMap<Integer,String>();
		hm.put(1, null); 
		//hm.put(null, "abc");  编译没错，运行报空指针异常  
		hm.put(1000, "aaa");
		hm.put(2, "bbb");
		hm.put(30000, "ccc");
		System.out.println(hm.containsValue("aaa"));
		System.out.println(hm.containsKey(30000));
		System.out.println(hm.get(30000));
		
		hm.put(30000, "ddd");  //更新覆盖ccc
		System.out.println(hm.get(30000));
		
		//hm.remove(2);
		System.out.println("size: " + hm.size());
		
		//hm.clear();
		//System.out.println("size: " + hm.size());
		
		System.out.println("遍历开始==================");
		
		Integer key;
		String value;
		Iterator<Entry<Integer, String>> iter = hm.entrySet().iterator();
		while(iter.hasNext()) {
		    Map.Entry<Integer, String> entry = iter.next();
		    // 获取key
		    key = entry.getKey();
		    // 获取value
		    value = entry.getValue();
		    System.out.println("Key:" + key + ", Value:" + value);
		}
		System.out.println("遍历结束==================");
		
		TreeMap<Integer,String> hm2 =new  TreeMap<Integer,String>();
		for(int i=0;i<100000;i++)
		{
			hm2.put(i, "aaa");
		}
		traverseByEntry(hm2);
		traverseByKeySet(hm2);		
	}
	
	public static void traverseByEntry(TreeMap<Integer,String> ht)
	{
		long startTime = System.nanoTime();
		System.out.println("============Entry迭代器遍历==============");
		Integer key;
		String value;
		Iterator<Entry<Integer, String>> iter = ht.entrySet().iterator();
		while(iter.hasNext()) {
		    Map.Entry<Integer, String> entry = iter.next();
		    // 获取key
		    key = entry.getKey();
		    // 获取value
		    value = entry.getValue();
		    //System.out.println("Key:" + key + ", Value:" + value);
		}
		long endTime = System.nanoTime();
	    long duration = endTime - startTime;
	    System.out.println(duration + "纳秒");
	}
	
	
	public static void traverseByKeySet(TreeMap<Integer,String> ht)
	{
		long startTime = System.nanoTime();
		System.out.println("============KeySet迭代器遍历=============="); 
		Integer key;
		String value;
		Iterator<Integer> iter = ht.keySet().iterator();
		while(iter.hasNext()) {
		    key = iter.next();		    
		    // 获取value
		    value = ht.get(key);
		    //System.out.println("Key:" + key + ", Value:" + value);
		}
		long endTime = System.nanoTime();
	    long duration = endTime - startTime;
	    System.out.println(duration + "纳秒");
	}
}