Here you can find the source of getFileSize(@Nonnull File file)
public static long getFileSize(@Nonnull File file)
//package com.java2s; /*//w ww . java 2 s . co m * Licensed to the Apache Software Foundation (ASF) under one * or more contributor license agreements. See the NOTICE file * distributed with this work for additional information * regarding copyright ownership. The ASF 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 * * 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. */ import java.io.File; import javax.annotation.Nonnull; public class Main { public static long getFileSize(@Nonnull File file) { if (!file.exists()) { return -1L; } long size = 0; if (file.isDirectory()) { File[] files = file.listFiles(); if (files != null && files.length > 0) { for (File f : files) { size += getFileSize(f); } } } else { size += file.length(); } return size; } }