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In Java, compound-assignment operators provide a shorter syntax for assigning the result of an arithmetic or bitwise operator. They perform the operation on two operands before assigning the result to the first operand. At run time, the expression is evaluated in one of two ways.Depending upon the programming conditions: First, the left-hand operand is evaluated to produce a variable. If this evaluation completes abruptly, then the assignment expression completes abruptly for the same reason; the right-hand operand is not evaluated and no assignment occurs. Otherwise, the value of the left-hand operand is saved and then the right-hand operand is evaluated. If this evaluation completes abruptly, then the assignment expression completes abruptly for the same reason and no assignment occurs. Otherwise, the saved value of the left-hand variable and the value of the right-hand operand are used to perform the binary operation indicated by the compound assignment operator. If this operation completes abruptly, then the assignment expression completes abruptly for the same reason and no assignment occurs. Otherwise, the result of the binary operation is converted to the type of the left-hand variable, subjected to value set conversion to the appropriate standard value set, and the result of the conversion is stored into the variable. First, the array reference sub-expression of the left-hand operand array access expression is evaluated. If this evaluation completes abruptly, then the assignment expression completes abruptly for the same reason; the index sub-expression (of the left-hand operand array access expression) and the right-hand operand are not evaluated and no assignment occurs. Otherwise, the index sub-expression of the left-hand operand array access expression is evaluated. If this evaluation completes abruptly, then the assignment expression completes abruptly for the same reason and the right-hand operand is not evaluated and no assignment occurs. Otherwise, if the value of the array reference sub-expression is null, then no assignment occurs and a NullPointerException is thrown. Otherwise, the value of the array reference sub-expression indeed refers to an array. If the value of the index sub-expression is less than zero, or greater than or equal to the length of the array, then no assignment occurs and an ArrayIndexOutOfBoundsException is thrown. Otherwise, the value of the index sub-expression is used to select a component of the array referred to by the value of the array reference sub-expression. The value of this component is saved and then the right-hand operand is evaluated. If this evaluation completes abruptly, then the assignment expression completes abruptly for the same reason and no assignment occurs. Note: Here, 6.6 which is double is automatically converted to short without explicit type-casting. Refer: When is the Type-conversion required? Now, we are going to understand the difference between normal assignment and compound assignment with the help of practical examples for better understanding.