Konvertierung von Bytes zu int in Java

Question

Ich muss 2 Bytes (2er Komplement) in einen Int in Java-Code konvertieren. wie mache ich es?

 
toInt(byte hb, byte lb) 
{ 

} 

Answer 1

return ((int)hb << 8) | ((int)lb & 0xFF); 

Der einwandfreie Betrieb in allen Fällen ist für den Schüler als Übung.

Answer 2

public int toInt(byte hb, byte lb) 
{ 
    return ((int)hb)<<8 + lb; 
} 

Answer 3

können Sie auch die ByteBuffer Klasse verwenden:

public int toInt(byte hb, byte lb) { 
    ByteBuffer bb = ByteBuffer.wrap(new byte[] {hb, lb}); 
    return bb.getShort(); // Implicitly widened to an int per JVM spec. 
} 

Diese Klasse könnte hilfreich sein, wenn Sie eine große Datenmenge Decodierung sind.

Answer 4

Verbrauch:

public class Test { 

    public static void main(String[] args) { 
     byte[] b = new byte[] { -83, 0, 0, 0 }; 

     int i = GattUtils.getIntValue(b, GattUtils.FORMAT_UINT32, 0); 

     System.out.println(i); //will print 173 
    } 


public class GattUtils { 
    public static final long leastSigBits = 0x800000805f9b34fbL; 

    public static final int FIRST_BITMASK = 0x01; 
    public static final int SECOND_BITMASK = FIRST_BITMASK << 1; 
    public static final int THIRD_BITMASK = FIRST_BITMASK << 2; 
    public static final int FOURTH_BITMASK = FIRST_BITMASK << 3; 
    public static final int FIFTH_BITMASK = FIRST_BITMASK << 4; 
    public static final int SIXTH_BITMASK = FIRST_BITMASK << 5; 
    public static final int SEVENTH_BITMASK = FIRST_BITMASK << 6; 
    public static final int EIGTH_BITMASK = FIRST_BITMASK << 7; 

    public static final int FORMAT_UINT8 = 17; 
    public static final int FORMAT_UINT16 = 18; 
    public static final int FORMAT_UINT32 = 20; 
    public static final int FORMAT_SINT8 = 33; 
    public static final int FORMAT_SINT16 = 34; 
    public static final int FORMAT_SINT32 = 36; 
    public static final int FORMAT_SFLOAT = 50; 
    public static final int FORMAT_FLOAT = 52; 

    public static UUID toUuid(String uuidString) { 
     return UUID.fromString(uuidString); 
    } 

    public static UUID toUuid(long assignedNumber) { 
     return new UUID((assignedNumber << 32) | 0x1000, leastSigBits); 
    } 

    public static String toUuid128(long assignedNumber) { 
     return toUuid(assignedNumber).toString(); 
    } 

    public static String toUuid16(int assignedNumber) { 
     return Integer.toHexString(assignedNumber); 
    } 

    public static Integer getIntValue(byte[] value, int format, int position) { 
     if (value == null) 
      return null; 
     if (position + (format & 0xF) > value.length) 
      return null; 
     switch (format) { 
     case FORMAT_UINT8: 
      return Integer.valueOf(value[position] & 0xFF); 
     case FORMAT_UINT16: 
      return Integer.valueOf(add(value[position], value[(position + 1)])); 
     case FORMAT_UINT32: 
      return Integer.valueOf(add(value[position], value[(position + 1)], value[(position + 2)], value[(position + 3)])); 
     case FORMAT_SINT8: 
      return Integer.valueOf(signed(value[position] & 0xFF, 8)); 
     case FORMAT_SINT16: 
      return Integer.valueOf(signed(add(value[position], value[(position + 1)]), 16)); 
     case FORMAT_SINT32: 
      return Integer.valueOf(signed(add(value[position], value[(position + 1)], value[(position + 2)], value[(position + 3)]), 32)); 
     } 
     return null; 
    } 

    public static Float getFloatValue(byte[] value, int format, int position) { 
     if (value == null) 
      return null; 
     if (position + (format & 0xF) > value.length) 
      return null; 
     int i; 
     int mantissa; 
     int exponent; 
     switch (format) { 
     case FORMAT_SFLOAT: 
      i = value[(position + 1)]; 
      position = value[position]; 
      mantissa = signed((position & 0xFF) + ((i & 0xFF & 0xF) << 8), 12); 
      exponent = signed((i & 0xFF) >> 4, 4); 
      return Float.valueOf((float) (mantissa * Math.pow(10.0D, exponent))); 
     case FORMAT_FLOAT: 
      exponent = value[(position + 3)]; 
      mantissa = value[(position + 2)]; 
      i = value[(position + 1)]; 
      position = value[position]; 
      return Float.valueOf((float) ((format = signed((position & 0xFF) + ((i & 0xFF) << 8) + ((mantissa & 0xFF) << 16), 24)) * Math.pow(10.0D, exponent))); 
     } 
     return null; 
    } 

    public static String getStringValue(byte[] value, int position) { 
     if (value == null) 
      return null; 
     if (position > value.length) 
      return null; 
     byte[] arrayOfByte = new byte[value.length - position]; 
     for (int i = 0; i != value.length - position; i++) { 
      arrayOfByte[i] = value[(position + i)]; 
     } 
     return new String(arrayOfByte); 
    } 

    private static int add(byte byte1, byte byte2) { 
     return (byte1 & 0xFF) + ((byte2 & 0xFF) << 8); 
    } 

    private static int add(byte byte1, byte byte2, byte byte3, byte byte4) { 
     return (byte1 & 0xFF) + ((byte2 & 0xFF) << 8) + ((byte3 & 0xFF) << 16) + ((byte4 & 0xFF) << 24); 
    } 

    private static int signed(int value, int length) { 
     if ((value & 1 << length - 1) != 0) 
      value = -1 * ((1 << length - 1) - (value & (1 << length - 1) - 1)); 
     return value; 
    } 

    /** 
    * Convert hex byte array from motorola API to byte array. 
    * 
    * @param hexByteArray 
    * @return 
    */ 
    public static byte[] hexByteArrayToByteArray(byte[] hexByteArray) { 
     return hexStringToByteArray(new String(hexByteArray)); 
    } 

    /** 
    * Convert string from motorola API to a byte array. 
    * 
    * @param hexString 
    * @return 
    */ 
    public static byte[] hexStringToByteArray(String hexString) { 
     int len = hexString.length(); 
     byte[] data = new byte[len/2]; 
     for (int i = 0; i < len; i += 2) { 
      data[i/2] = (byte) ((Character.digit(hexString.charAt(i), 16) << 4) + Character.digit(hexString.charAt(i + 1), 16)); 
     } 
     return data; 
    } 
}