The unary plus operator (+) is used in the form
+operand
The operand must be a primitive numeric type.
If the operand is of the byte, short, or char type, the unary plus operator promotes it to int type.
byte b1 = 10; byte b2 = +5; b1 = b2; // Ok. byte to byte assignment
In the following code, b2 is of the type byte. unary plus operator on b2 promoted its type to int. +b2 is of the type int. int to byte assignment is not allowed.
byte b1 = 10; byte b2 = +5; b1 = +b2; // A compile-time error.
To fix the error, add casting.
b1 = (byte) +b2; // Ok