Java Integer Create toInteger(byte[] b)

Description

Convert a 4 bytes array into an integer number.

License

Open Source License

Parameter

Parameter	Description
b	A 4 bytes array.

Exception

Parameter	Description
NullPointerException	b is null.
IllegalArgumentException	The length of b is not 4.

Return

An integer number.

Declaration

public static int toInteger(byte[] b) 

Method Source Code

//package com.java2s;
/*//ww  w. j  a v  a 2 s. c om
 * Copyright (c) 2015 NEC Corporation
 * All rights reserved.
 *
 * This program and the accompanying materials are made available under the
 * terms of the Eclipse Public License v1.0 which accompanies this
 * distribution, and is available at http://www.eclipse.org/legal/epl-v10.html
 */

public class Main {
    /**
     * The number of octets in an integer value.
     */
    public static final int NUM_OCTETS_INTEGER = Integer.SIZE / Byte.SIZE;
    /**
     * A mask value which represents all bits in a byte value.
     */
    public static final int MASK_BYTE = (1 << Byte.SIZE) - 1;
    /**
     * The number of bits to be shifted to get the first octet in an integer.
     */
    private static final int INT_SHIFT_OCTET1 = 24;
    /**
     * The number of bits to be shifted to get the second octet in an integer.
     */
    private static final int INT_SHIFT_OCTET2 = 16;
    /**
     * The number of bits to be shifted to get the third octet in an integer.
     */
    private static final int INT_SHIFT_OCTET3 = 8;

    /**
     * Convert a 4 bytes array into an integer number.
     *
     * @param b  A 4 bytes array.
     * @return   An integer number.
     * @throws NullPointerException
     *    {@code b} is {@code null}.
     * @throws IllegalArgumentException
     *    The length of {@code b} is not 4.
     */
    public static int toInteger(byte[] b) {
        if (b.length != NUM_OCTETS_INTEGER) {
            throw new IllegalArgumentException("Invalid byte array length: " + b.length);
        }

        int index = 0;
        int value = (b[index++] & MASK_BYTE) << INT_SHIFT_OCTET1;
        value |= (b[index++] & MASK_BYTE) << INT_SHIFT_OCTET2;
        value |= (b[index++] & MASK_BYTE) << INT_SHIFT_OCTET3;
        return value | (b[index] & MASK_BYTE);
    }

    /**
     * Convert the given number into a {@link Integer} instance.
     *
     * @param num  A {@link Number} instance.
     * @return  An {@link Integer} instance equivalent to the given number.
     *          {@code null} if {@code num} is {@code null}.
     */
    public static Integer toInteger(Number num) {
        return (num == null) ? null : Integer.valueOf(num.intValue());
    }
}

Related

1. toInteger(boolean bool)
2. toInteger(boolean bool)
3. toInteger(boolean bool)
4. toInteger(byte b1, byte b2, byte b3, byte b4)
5. toInteger(byte[] b)
6. toInteger(byte[] bytes)
7. toInteger(byte[] bytes)
8. toInteger(byte[] bytes, int index)
9. toInteger(byte[] input)