通过Java代码实现对象、List类集、数组、Map及常用数据类型等占用字节大小的代码示例，详情参见代码示例部分。

package Test;

import java.io.ByteArrayOutputStream;
import java.io.ObjectOutputStream;
import java.util.HashMap;
import java.util.List;

public class ByteSizeUtil {
	
	
	/**
	 * @desc  对象、List类集、数组、Map及常用数据类型等占用字节大小
	 * @param 
	 * @return
	 */
	 public static   int  getByteSize( HashMap<String,Object> hashMap){
        int byteSize=0;
        try {
            ByteArrayOutputStream baos = new ByteArrayOutputStream();  
            ObjectOutputStream os = new ObjectOutputStream(baos);  
            os.writeObject(hashMap);  
            os.close(); 
            byteSize=baos.size();
            System.out.println("所占字节  "+byteSize+" 字节");
            //System.out.println("所占"+byteSize/1024+" KB");
            baos.close();
        } catch (Exception e) {
            e.printStackTrace();
        }  
        return byteSize;
     }
	 
	 
	 public  static  int  getByteSize(List<Integer>  datas) {
	        int byteSize=0;
	        try {
	            ByteArrayOutputStream baos = new ByteArrayOutputStream();  
	            ObjectOutputStream os = new ObjectOutputStream(baos);  
	            os.writeObject(datas);  
	            os.close(); 
	            byteSize=baos.size();
	            System.out.println("所占字节  "+byteSize+" 字节");
	            baos.close();
	        } catch (Exception e) {
	            e.printStackTrace();
	        }  
	        return byteSize;
	    }
	
	
	    public static <V> void main(String[] args) throws  Exception{
	        int n = 2021;  
	        HashMap<String,Object> hashMap = new HashMap<String, Object>();
	        //测试添加数据
	        for (int i = 0; i < n; i++) {  
	        	hashMap.put(String.valueOf(n), n);
	        }  
	        getByteSize(hashMap);
	    }
}