Hexadecimal enumeration types use java to return wrong values?

I use the following enumeration types in the following code:

public static enum PanelType
 {
   PAS8((byte)0xA6),PAS83((byte)0xA7);

  private byte code;

  private PanelType(byte code)
  {
   this.code=code;
  }

  public byte getCode(){
   return code;
  }
 }

However, when I try to use it in my method:

for (PanelType type:PanelType.values())
 {
   if (decoded[3]==type.getCode())
   return type;
 }

I will return: type Error value of getcode () method It returns - 90 instead of 166, which is exactly what I expected

I know ffff ffff ffff ffa6 = - 90, but why does 0xa6 return as a negative number?

Solution

The maximum value of bytes is 127 and the minimum value is - 128 0xa6 is decimal 166, so there is an overflow:

-128 + (166 - 127 - 1) == -90