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DigestUtils
package bluexmas.utils;
import java.io.FileNotFoundException;
import java.io.RandomAccessFile;
import java.security.MessageDigest;
import java.security.NoSuchAlgorithmException;
public class DigestUtils {
public static String extractStringHashSHA256(String str){
String SHA = "";
try{
MessageDigest sh = MessageDigest.getInstance("SHA-256");
sh.update(str.getBytes());
byte byteData[] = sh.digest();
StringBuffer sb = new StringBuffer();
for(int i = 0 ; i < byteData.length ; i++){
sb.append(Integer.toString((byteData[i]&0xff) + 0x100, 16).substring(1));
}
SHA = sb.toString();
}catch(NoSuchAlgorithmException e){
e.printStackTrace();
SHA = null;
}
return SHA;
}
public static String extractFileHashSHA256(String filename) throws Exception {
String SHA = "";
int buff = 16384;
try {
RandomAccessFile file = new RandomAccessFile(filename, "r");
MessageDigest hashSum = MessageDigest.getInstance("SHA-256");
byte[] buffer = new byte[buff];
byte[] partialHash = null;
long read = 0;
// calculate the hash of the hole file for the test
long offset = file.length();
int unitsize;
while (read < offset) {
unitsize = (int) (((offset - read) >= buff) ? buff : (offset - read));
file.read(buffer, 0, unitsize);
hashSum.update(buffer, 0, unitsize);
read += unitsize;
}
file.close();
partialHash = new byte[hashSum.getDigestLength()];
partialHash = hashSum.digest();
StringBuffer sb = new StringBuffer();
for(int i = 0 ; i < partialHash.length ; i++){
sb.append(Integer.toString((partialHash[i]&0xff) + 0x100, 16).substring(1));
}
SHA = sb.toString();
} catch (FileNotFoundException e) {
e.printStackTrace();
}
return SHA;
}
public static void main(String[] args) throws Exception {
System.out.println(extractStringHashSHA256("1"));
System.out.println(extractFileHashSHA256("a.pdf"));
}
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