package test;import java.util.HashMap;import java.util.Map;public class TestMemory {    public static void main(String[] args) {        System.gc();        long total = Runtime.getRuntime().totalMemory(); // byte        long m1 = Runtime.getRuntime().freeMemory();        System.out.println("before:" + (total - m1));                 Map
    
      map = new HashMap
     
      ();        for(int i=0; i < 1e6; i++){            map.put(new Double(Math.random()*1e9), new Double(Math.random()*1e10));        }        long total1 = Runtime.getRuntime().totalMemory();        long m2 = Runtime.getRuntime().freeMemory();        System.out.println("after:" + (total1 - m2));//        System.out.println(map.toString());        System.exit(0);    }}