ICS3U-Arithmetic in Java

In Java, doing simple arithmetic is very much like doing arithmetic in other languages such as Qbasic and Pascal using the +, -, * and / operators (plus, minus, times and divide). Often times, you will store the result of the mathematical expression in a variable. This is where the assignment operator is used.

The Assignment Operator (=)

• The assignment operator (=) causes the operand (the variable) on the left side of the assignment operator to have its value changed to the value on the right side of the assignment operator.

For example the expression ...

x = y + z;

• Assigns the value that is the result of adding y and z to the operand (variable) x
• Don't confuse the assignment operator (=) with the test for equivalence (==).

Math Operators (+, -, /, *, %)

• Multiplication, addition and subtraction work as you would expect.
• Integer division is a little different from everyday division because of the fact that computers can lose information due to precision constraints. For example, when you divide 27 by 5, the result is a real number (a number with a decimal component). Integers don't have a decimal component (or a fraction component) and so the "remainder" is discarded.
• The division of two integers like 27 divided by 5 will result in an answer of 5.
• The modulus operator tells you the remainder after an integer division. To find the remainder of the division of two integers like 27 divided by 5, you would use the modulus division operator %.You would do this by calculating 27 modulus 5 (27 % 5) and you would get the result 2.

Auto-incrementing and Auto-decrementing Variables

The most common mathematical formula used in programming languages is to take a variable add (or subtract) the value 1 to it and then store the result in the same variable.

In Java and many other programming Languages...

• increasing a value by 1 is called incrementing, and
• decreasing by 1 is called decrementing.

There are special operators to perform these actions.

• The increment operator (++) increases the value of the variable by 1,
• The decrement operator (--) decreases the value of the variable by 1.

For example:

1) if you have a variable x and you want to increment it, you would use this statement:

x++;   // increases the value stored in x by one    // This is the same as the statement x=x+1;

2) if you have a variable x and you want to decrement it, you would use this statement:

x--;   // decreases the value stored in x by one    // This is the same as the statement x=x-1;

Self-Assign operators

• In Java (like in C++ and many other languages) it is a common event to add a value to a variable, and then to assign the result back into that same variable (like the x++ example shown above). A simple way to do this is to write the expression using a self-assign operator.
• The self-assigned addition operator (+=) adds the rvalue to the lvalue and then reassigns the result into the lvalue. This operator is pronounced "plus-equals." The statement would be read "myAge plus-equals two." If myAge had the value 4 to start, it would have 6 after this statement.

There are several self-assign operators ...

Example:

myMark += 10;

If myMark had the value 80 to start, it would have 90 after this statement was executed.