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Learn Java: Manipulating Variables
Compound Assignment Operators

Sometimes, we need to adjust the value of a variable.

Imagine we’re working at a bake sale and want to keep track of how many cupcakes we have by creating a variable called numCupcakes:

int numCupcakes = 12;

If we baked 8 more cupcakes, we know that we could update our variable using the + operator:

numCupcakes = numCupcakes + 8; // Value is now 20

While this method works just fine, we had to write our variable numCupcakes twice. We can shorten this syntax by using a compound assignment operator.

Compound assignment operators perform an arithmetic operation on a variable and then reassigns its value. Using the += compound assignment operator, we can rewrite our previous code like so:

numCupcakes += 8; // Value is now 20

Now we only need to reference numCupcakes once.

We can use compound assignment operators for all of the arithmetic operators we’ve covered:

  • Addition (+=)
  • Subtraction (-=)
  • Multiplication (*=)
  • Division (/=)
  • Modulo (%=)

Instructions

1.

You are also in charge of keeping track of how many cookies there are at the bake sale. This value is represented by the variable numCookies.

A customer comes and buys 3 cookies. Use the appropriate compound assignment operator to reflect this change.

2.

Another customer buys half of the remaining cookies.

Use the appropriate compound assignment operator to reflect this change.

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