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The Java language supports various arithmetic operators for all floating-point and integer numbers. These include+
(addition),-
(subtraction),*
(multiplication),/
(division), and%
(modulo). For example, you can use this Java code to add two numbers:Or you can use the following Java code to compute the remainder that results from dividingaddThis + toThisdivideThis
bybyThis
:divideThis % byThisThis table summarizes Java's binary arithmetic operations:
Operator Use Description +
op1 + op2
Adds op1
andop2
-
op1 - op2
Subtracts op2
fromop1
*
op1 * op2
Multiplies op1
byop2
/
op1 / op2
Divides op1
byop2
%
op1 % op2
Computes the remainder of dividing op1
byop2
Note: The Java language extends the definition of the+
operator to include string concatenation. You'll see more about this in Arrays and Strings.
The
+
and-
operators have unary versions that perform the following operations:
Operator Use Description +
+op
Promotes op
toint
if it's abyte
,short
, orchar
-
-op
Arithmetically negates op
There also are two short cut arithmetic operators,
++
which increments its operand by 1, and--
which decrements its operand by 1. Either++
or--
can appear before (prefix) or after (postfix) its operand. The prefix version,++op
/--op
, evaluates to the value of the operand after the increment/decrement operation. The postfix version,op++
/op--
, evaluates the value of the operand before the increment/decrement operation.Recall the
Sort
program.
Let's look at how thepublic class Sort { public static void main(String[] args) { int[] arrayOfInts = { 32, 87, 3, 589, 12, 1076, 2000, 8, 622, 127 }; for (int i = arrayOfInts.length; --i >= 0; ) { for (int j = 0; j < i; j++) { if (arrayOfInts[j] > arrayOfInts[j+1]) { int temp = arrayOfInts[j]; arrayOfInts[j] = arrayOfInts[j+1]; arrayOfInts[j+1] = temp; } } } for (int i = 0; i < arrayOfInts.length; i++) { System.out.print(arrayOfInts[i] + " "); } System.out.println(); } }Sort
program uses--
to control the outer of its two nested sorting loops. Here's the statement that controls the outer loop:The return value of the operationfor (int i = arrayOfInts.length; --i >= 0; ) { ... }--i
is compared to 0 to determine whether to terminate the loop. Using the prefix version of--
means that the last iteration of this loop occurs wheni
is equal to 0. If we changed the code to use the postfix version of--
, the last iteration of this loop occurs wheni
is equal to -1, which is incorrect for this program.The other two loops in the program use the the postfix version of
++
. In both cases, the version used doesn't really matter because the value returned by the operator isn't used for anything.The short cut increment/decrement operators are summarized in the following table:
Operator Use Description ++
op++
Increments op
by 1; evaluates to the value of op before it was incremented++
++op
Increments op
by 1; evaluates to the value of op after it was incremented--
op--
Decrements op
by 1; evaluates to the value of op before it was decremented--
--op
Decrements op
by 1; evaluates to the value of op after it was decremented
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