java 文件读写工具 FileUtil

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;
}
}