Here you can find the source of getUsedMemory()
public static long getUsedMemory()
//package com.java2s; /*/*ww w.j a v a2 s. co m*/ * Copyright (c) 2014, Cloudera, Inc. All Rights Reserved. * * Cloudera, Inc. licenses this file to you 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 * * This software 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 { /** * @return approximate heap used, in bytes */ public static long getUsedMemory() { Runtime runtime = Runtime.getRuntime(); return runtime.totalMemory() - runtime.freeMemory(); } }