Calculates the given file's SHA-1 hash code. - Java Security

Java examples for Security:DSA

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Description

Calculates the given file's SHA-1 hash code.

Demo Code

/**//from ww w.  ja va2  s. co m
 * Copyright (C) 2012 White Source Ltd.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 * http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
//package com.java2s;
import java.io.File;
import java.io.FileInputStream;
import java.io.IOException;
import java.security.MessageDigest;
import java.security.NoSuchAlgorithmException;

public class Main {
    public static void main(String[] argv) throws Exception {
        File resourceFile = new File("Main.java");
        System.out.println(calculateSHA1(resourceFile));
    }

    private static final int BUFFER_SIZE = 32 * 1024;

    /**
     * Calculates the given file's SHA-1 hash code.
     *
     * @param resourceFile File to calculate
     *
     * @return Calculated SHA-1 for the given file.
     *
     * @throws IOException on file reading errors.
     * @throws IllegalStateException when no algorithm for SHA-1 can be found.
     */
    public static String calculateSHA1(File resourceFile)
            throws IOException {

        MessageDigest messageDigest;
        try {
            messageDigest = MessageDigest.getInstance("SHA-1");
        } catch (NoSuchAlgorithmException e) {
            throw new IllegalStateException(e.getMessage(), e);
        }

        FileInputStream fis = new FileInputStream(resourceFile);
        byte[] buffer = new byte[BUFFER_SIZE];
        try {
            int len = fis.read(buffer, 0, BUFFER_SIZE);
            while (len >= 0) {
                messageDigest.update(buffer, 0, len);
                len = fis.read(buffer, 0, BUFFER_SIZE);
            }
        } finally {
            try {
                fis.close();
            } catch (IOException e) {
                // ignore
            }
        }

        return toHex(messageDigest.digest());
    }

    private static String toHex(byte[] bytes) {
        StringBuilder sb = new StringBuilder(bytes.length * 2);

        for (byte aByte : bytes) {
            int b = aByte & 0xFF;
            if (b < 0x10) {
                sb.append('0');
            }
            sb.append(Integer.toHexString(b));
        }

        return sb.toString();
    }
}

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