检查给定的路径是否为File，是否不存在（除非allowOverwrite为true）并且可写
/** * Copyright 2011-2012 Cray Inc. All Rights Reserved * * Redistribution and use in source and binary forms, with or without * modification, are permitted provided that the following conditions are * met: * * * Redistributions of source code must retain the above copyright * notice, this list of conditions and the following disclaimer. * * * Redistributions in binary form must reproduce the above copyright * notice, this list of conditions and the following disclaimer in the * documentation and/or other materials provided with the distribution. * * * Neither the name Cray Inc. nor the names of its contributors may be * used to endorse or promote products derived from this software * without specific prior written permission. * * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. **/ //package com.nowjava; import java.io.File; /** 来自 时代Java公众号**/ import java.io.FileWriter; public class Main { public static void main(String[] argv) throws Exception { String filename = "nowjava.com"; boolean allowOverwrite = true; System.out.println(checkFile(filename, allowOverwrite)); } /** * Checks whether a given path is a File, does not exist (unless {@code allowOverwrite} is true) and is writable * @param filename Filename to check * @param allowOverwrite Whether overwriting of existing files is allowed * @return True if the file is usable, false otherwise */ public static boolean checkFile(String filename, boolean allowOverwrite) { File f = new File(filename); //Must not exist or allowOverwrite must be true/** from 时 代 J a v a 公 众 号 - nowjava.com**/ if (f.exists() && !allowOverwrite) return false; //Must be a File if it exists (need exists check because isFile() will return false if path doesn't exist)