java 文件读写工具 FileUtil

代码如下：

package com.wiscom.utils;

import java.io.BufferedReader;
import java.io.File;
import java.io.FileInputStream;
import java.io.FileNotFoundException;
import java.io.FileWriter;
import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.io.Reader;
import java.io.UnsupportedEncodingException;

public class FileUtil {
    
    /**
     *  以字节为单位读取文件，通常用于读取二进制文件，如图片
     * @param path
     * @return
     */
    public static String readByBytes(String path) {    
        String content = null;
        
        try {
            InputStream inputStream = new FileInputStream(path);
            StringBuffer sb = new StringBuffer();
            int c = 0;
            byte[] bytes = new byte[1024];
            /*
             * InputStream.read(byte[] b)
             * 
             * Reads some number of bytes from the input stream and stores them into the buffer array b. 从输入流中读取一些字节存入缓冲数组b中
             * The number of bytes actually read is returned as an integer.  返回实际读到的字节数
             * This method blocks until input data is available, end of file is detected, or an exception is thrown. 
             * 该方法会一直阻塞，直到输入数据可以得到、或检测到文件结束、或抛出异常  -- 意思是得到数据就返回
             */
            while ((c = inputStream.read(bytes)) != -1) {
                sb.append(new String(bytes, 0, c, "utf-8"));
            }
            
            content = sb.toString();
            inputStream.close();
        } catch (FileNotFoundException e) {
            e.printStackTrace();
        } catch (IOException e) {
            e.printStackTrace();
        }
        
        return content;
    } 
    
    /**
     *  以行为单位读取文件，常用于读取面向行的格式化文件
     * @param path
     * @return
     */
    public static String readByLines(String path) {
        String content = null;
        
        
        try {
            BufferedReader bufferedReader = new BufferedReader(new InputStreamReader(new FileInputStream(path), "utf-8"));
            
            StringBuffer sb = new StringBuffer();
            String temp = null;
            while ((temp = bufferedReader.readLine()) != null) {
                sb.append(temp);
            }
            
            content = sb.toString();
            bufferedReader.close();
        } catch (UnsupportedEncodingException  e) {
            e.printStackTrace();
        } catch (IOException e) {
            e.printStackTrace();
        }
        
        return content;
    }
    
    /**
     *  以字符为单位读取文件，常用于读取文本文件
     * @param path
     * @return
     */
    public static String readByChars(String path) {
        String content = null;
        
        try {
            
            Reader reader = new InputStreamReader(new FileInputStream(path), "utf-8");
            StringBuffer sb = new StringBuffer();
            

            char[] tempchars = new char[1024];
            while (reader.read(tempchars) != -1) {
                sb.append(tempchars);
            }
            
            content = sb.toString();
            reader.close();    
        } catch (Exception e) {
            e.printStackTrace();
        }    
        return content;
    }
    
    /**
     *  把内容content写的path文件中
     * @param content
     * @param path
     * @return
     */
    public static boolean saveAs(String content, String path) {
        
        FileWriter fw = null;
        
        //System.out.println("把内容：" + content + "， 写入文件："  + path);
        
        try {
            /**
             * Constructs a FileWriter object given a File object. 
             * If the second argument is true, then bytes will be written to the end of the file rather than the beginning.
             * 根据给定的File对象构造一个FileWriter对象。 如果append参数为true, 则字节将被写入到文件的末尾（向文件中追加内容）
             *
             *    Parameters:
             *        file,  a File object to write to 带写入的文件对象
             *        append,  if true, then bytes will be written to the end of the file rather than the beginning
             *    Throws:
             *        IOException - 
             *        if the file exists but is a directory rather than a regular file, 
             *            does not exist but cannot be created, 
             *            or cannot be opened for any other reason
             *      报异常的3种情况：
             *          file对象是一个存在的目录（不是一个常规文件）
             *          file对象是一个不存在的常规文件，但不能被创建
             *          file对象是一个存在的常规文件，但不能被打开
             *
             */
            fw = new FileWriter(new File(path), false);
            if (content != null) {
                fw.write(content);
            }    
        } catch (IOException e) {
            e.printStackTrace();
            return false;
        } finally {
            if (fw != null) {
                try {
                    fw.flush();
                    fw.close();
                } catch (IOException e) {
                    e.printStackTrace();
                }
            }
        }
        return true;
    }
}