Operator precedence

"Hi, Bilaabo!"

"Bilaabo is happy to greet his friend!"

"Today Bilaabo will tell you about operator precedence. But first he will tell you about the operators themselves."

"What are these operators you speak of?"

"Actually, you're already familiar with them. You just might not have known they are called operators."

"For example, say we have the expression c = a + b;"

"It has two operators: an addition operator and an assignment operator."

"In other words, operators are just mathematical signs? Like multiplication, division, and addition?"

"Yes, that is true. However, there are differences."

"I won't define operators for you: a definition won't make you smarter. It's better to see them in action. Operators can be divided into several groups, which we'll examine now."

1) "Mathematical operators"

"I recognize these from school. My firmware includes school courses."

"But, what's with that percent sign, some sort of wizardry?"

"It's the "remainder after division" operator. If 11 is divided by 5, then we get 2 and a remainder of 1. This 1 can be obtained by writing 11 % 5;"

"When you divide integers in Java, the result is also an integer. The remainder from the division operation is simply ignored. If we divide 8 by 5, we get 1."

"But what in the world do we need the remainder for?"

"Suppose you need to check whether an integer is even. Then you can write:"

if (a % 2 == 0)

"And if you need to check if b is odd, then you can write:"

if (b % 2 == 1)

"Or to check whether d is divisible by 3:"

if (d % 3 == 0)

"Interesting. I'll remember that."

2)  "Comparison operators"

"I already use all of these."

"And what's the main difference between these operators and the mathematical operators?"

"If we add two numbers, we get a number; but, if we compare two numbers, we get true or false."

"That's right. The result of a comparison is a "logical value" value, which, as you know, is represented by the boolean type. There are two possibilities: true or false.

"Yep, that's all clear. I know that already."

3) "Logical operators"

"Logical operators can only be used with boolean variables or expressions."

"I know all this already."

"Really? Let's carry on, then."

4) "Bitwise operators"

"Bitwise operators perform bit-by-bit operations on integers."

"What's that?"

"Each number is represented as a set of bits, and then the result is calculated as follows:"

"If the first bit of both numbers is 1, then the result's first bit will be 1."

"If the second bit of both numbers is 1, then the result's second bit will be 1. And so on."

"Is that true for all bitwise operators?"

"It's a lot simpler than that. A bit can only have two values, 0 and 1, right?"

"Right."

"Then think of 1 as true, and 0 as false. Operations on individual bits will then be nearly identical to logical operations:"

"Oh! That's so easy."

"Yes, just don't forget that bitwise operations use corresponding bits from two numbers."

"Yes, I remember: the first bit of one number is paired with the first bit of the second, and the result is also written to the first bit. And the same goes for the rest of the bits."

"That's right. Do you have any other questions?"

"What's with the XOR and 'exclusive or'?"

"It's a piece of cake: when the values are different, it's true; when they are the same, it's false."

Here are a couple more examples of bitwise operations:

"Thank you, Bilaabo. Now I know."

"There is one more group of bitwise operators, the shift operators:"

5) "Shift operators"

"What kind of street magic is this?"

"It's actually all really simple. Check it out:"

"Shifting a number's bits to the left by 1 is the same as multiplying the number by 2. Shifting by two digits is equivalent to multiplication by 4, by three digits — multiplication by 8, and so on."

"Shifting right corresponds to dividing by 2, 4, 8, 16, etc."

"But what's the difference between the >>> and >> operators?"

"They differ when working with negative numbers. This is because signed numbers use the leftmost bit to indicate the sign. As a result, a negative number ceases to be negative when shifting to the right. So, they came up with two different operators. Check it out:"

"The shift is not cyclic. Bits that move beyond the left or right edge of the number are simply discarded."

6) "Assignment operators"

"I already know what assignment is. But why do you say 'operators'?"

"Because there are several of them ☺"

"I think you get the logic."

7) "Increment and decrement operators"

"Is there a difference between putting the two minus signs before or after the variable?"

"Yes, there is, though not very big. If a variable with one of these operators is a part of an expression or assignment, then there are differences. I'd rather show you by example:"

"Whoa! That's cool!"

"I'm glad you liked it. But, if there is no expression or assignment, then there are no differences:"

"x++ is equivalent to x = x + 1."

"++x is equivalent to x = x + 1."

"I'll keep that in mind. Thanks, Bilaabo."

8) "Ternary operator"

"This operator doesn't just use one or two variables or expressions. It uses three variables or expressions all at once:"

"Well, that's super convenient."

"Yes. And it's compact and the code is readable. Enjoy using it!"

9) "Other"

"No matter how well organized your music collection, you still have to create a "Miscellaneous" folder."

"Yeah, anyone who's ever had to categorize music would totally agree."

"So, there are three more operators I want to tell you about:"

"And, finally, here's a table that summarizes operator precedence:"