The result of java expression "a"+20 is: A = (data type of A) (A"+20). The assignment operator has forced the result: a+= 20; Equivalent to a = (data type of a) (a+20); Therefore, after byte/short participates in the assignment operation, the operation result is still the original type. Expressions connected by operators, constants, variables and methods in Java are called expressions. There are three kinds of Java operators: arithmetic operator, bitwise operator, relational operator (comparison operator), logical operator, ternary operator and assignment operator.