java 两个文件对比_Java 判断两个文件是否相同

使用Java 如何判断两个文件是否相同呢？我的做法是

(1)先比较两个文件内容的长度；

(2)在长度相同的情况下，再比较两个文件的MD5值。

需要引入的Jar 包：

commons-codec

commons-codec

1.11

先提供一个验证两个文件字节流是否一致的函数：

/*** 验证两个文件字节流是否相等

*@returnboolean true 相等

*@throwsIOException*/

private static boolean isSameFiles(byte[] fileByte1, byte[] fileByte2) {

String firstFileMd5=DigestUtils.md5Hex(fileByte1);

String secondFileMd5=DigestUtils.md5Hex(fileByte2);if(firstFileMd5.equals(secondFileMd5)) {

System.out.println("---- equals ------ md5 " +firstFileMd5);return true;

}else{

System.out.println(firstFileMd5+ " is firstFileMd5 ++ unequal ++ secondFileMd5 = " +secondFileMd5);return false;

}

}

1 校验base64 位字符串形式的文件是否相等

直接把字符串转成字节数组，然后调用isSameFiles函数。

public static void main(String[] args) throwsIOException {//TODO Auto-generated method stub

String img = "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";

String imgReal= "iVBOI=";

BASE64Decoder decoder= newBASE64Decoder();if(isBase64(img)) {

System.out.println("img is base 64");

}if(isBase64(imgReal)) {

System.out.println("imgReal is base 64");

}byte[] imageByteArray = null;try{

imageByteArray=decoder.decodeBuffer(img);

System.out.println(isSameFiles(imageByteArray, decoder.decodeBuffer(imgReal)));

}catch(IOException e) {

e.printStackTrace();

}

System.out.println(chechFile());

}

/**

* 校验字符串是否为base64 的

*

* @param str

* @return

*/

private static boolean isBase64(String str) {

String base64Pattern = "^([A-Za-z0-9+/]{4})*([A-Za-z0-9+/]{4}|[A-Za-z0-9+/]{3}=|[A-Za-z0-9+/]{2}==)$";

return Pattern.matches(base64Pattern, str);

}

2 校验两个文件是否相等

读取文件后，将其转换成字节流：

/*** 检查两个文件是否相等，假设 C:\Users\Pictures目录下有两个图片文件

*@returnboolean true 相等

*@throwsIOException*/

private static boolean chechFile() throwsIOException {

File file1= new File("C:\\Users\\Pictures\\test1.jpg");

File file2= new File("C:\\Users\\Pictures\\test2.jpg");if (file1.length() !=file2.length()) {

System.out.println("+++++++++ unequal +++++++++++++");return false;

}

InputStream fileStream1= newFileInputStream(file1);

InputStream fileStream2= newFileInputStream(file2);//InputStream 转 byte[]

byte[] imageByteArray = new byte[fileStream1.available()];

System.out.println(isSameFiles(imageByteArray,new byte[fileStream2.available()]));return true;

}

以上方法验证小文件妥妥的，大文件请移步：《JAVA MD5 验证大文件(改)》

Reference

https://www.cnblogs.com/DylanZ/p/6269042.html