Here you can find the source of usedMemory()
public static long usedMemory()
//package com.java2s; /******************************************************************************* * Copyright (C) 2014 Dell, Inc./* w ww . jav a 2 s .c o m*/ * * Licensed under the Apache License, Version 2.0 (the "License"); you may not use this file except in compliance with * the License. You may obtain a copy of the License at * * http://www.apache.org/licenses/LICENSE-2.0 * * Unless required by applicable law or agreed to in writing, software distributed under the License is distributed on * an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the License for the * specific language governing permissions and limitations under the License. *******************************************************************************/ public class Main { private static final Runtime RUNTIME = Runtime.getRuntime(); public static long usedMemory() { return RUNTIME.totalMemory() - RUNTIME.freeMemory(); } }