在java后台判断两个文件是否是同一文件

// 计算文件的 MD5 值 根据MD5值 判断文件是否是同一个文件
public static String getFileMD5(File file) {
if (!file.isFile()) {
return null;
}
MessageDigest digest = null;
FileInputStream in = null;
byte buffer[] = new byte[8192];
int len;
try {
digest =MessageDigest.getInstance("MD5");
in = new FileInputStream(file);
while ((len = in.read(buffer)) != -1) {
digest.update(buffer, 0, len);
}
BigInteger bigInt = new BigInteger(1, digest.digest());
return bigInt.toString(16);
} catch (Exception e) {
e.printStackTrace();
return null;
} finally {
try {
in.close();
} catch (Exception e) {
e.printStackTrace();
}
}

}

// 计算文件的 SHA-1 值 根据SHA-1值 判断文件是否是同一个文件
public static String getFileSha1(File file) {
if (!file.isFile()) {
return null;
}
MessageDigest digest = null;
FileInputStream in = null;
byte buffer[] = new byte[8192];
int len;
try {
digest =MessageDigest.getInstance("SHA-1");
in = new FileInputStream(file);
while ((len = in.read(buffer)) != -1) {
digest.update(buffer, 0, len);

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}
BigInteger bigInt = new BigInteger(1, digest.digest());
return bigInt.toString(16);
} catch (Exception e) {
e.printStackTrace();
return null;
} finally {
try {
in.close();
} catch (Exception e) {
e.printStackTrace();
}
}
}

public class  IOOperation
{
public static void main(String[] args)
{
FileInputStream File1 = null;
FileInputStream File2 = null;
BufferedReader in = null;
String sFile;

if(args.length != 2)
{
System.out.println("The command line should be: java IOOperation testX.txt testX.txt");
System.out.println("X should be one of the array: 1, 2, 3");
System.exit(0);
}

try
{
File1 = new FileInputStream(args[0]);
File2 = new FileInputStream(args[1]);

try
{

if(File1.available() != File2.available())
{
//长度不同内容肯定不同
System.out.println(args[0] + " is not equal to " + args[1]);
}
else
{
boolean tag = true;

while( File1.read() != -1 && File2.read() != -1)
{
if(File1.read() != File2.read())
{
tag = false;
break;
}
}

if(tag == true)
System.out.println(args[0] + " equals to " + args[1]);
else
System.out.println(args[0] + " is not equal to " + args[1]);
}
}
catch(IOException e)
{
System.out.println(e);
}
}
catch (FileNotFoundException e)
{
System.out.println("File can't find..");
}
finally
{

try
{
if(File1 != null)
File1.close();
if(File2 != null)
File2.close();
}
catch (IOException e)
{
System.out.println(e);
}
}
}