Operators are special symbols that perform specific operations on one, two, or three operands, and then return a result
The operators in the following table are listed according to precedence order.
The closer to the top of the table an operator appears, the higher its precedence.
Operators with higher precedence are evaluated before operators with relatively lower precedence.
Operators on the same line have equal precedence. When operators of equal precedence appear in the same expression, a rule must govern which is evaluated first.
All binary operators except for the assignment operators are evaluated from left to right; assignment operators are evaluated right to left.
| Operators | Precedence |
|---|---|
| postfix | expr++ expr-- |
| unary | ++expr --expr +expr -expr ~ ! |
| multiplicative | * / % |
| additive | + - |
| shift | << >> >>> |
| relational | < > <= >= instanceof |
| equality | == != |
| bitwise AND | & |
| bitwise exclusive OR | ^ |
| bitwise inclusive OR | | |
| logical AND | && |
| logical OR | || |
| ternary | ? : |
| assignment | = += -= *= /= %= &= ^= |= <<= >>= >>>= |
In general-purpose programming, certain operators tend to appear more frequently than others; for example, the assignment operator "=" is far more common than the unsigned right shift operator ">>>".
Assignment operator - It assigns the value on its right to the operand on its left:
int cadence = 0;
int speed = 0;
int gear = 1;
The Arithmetic Operators - The Java programming language provides operators that perform addition, subtraction, multiplication, and division.
The symbol "%", which divides one operand by another and returns the remainder as its result.
| Operator | Description |
|---|---|
+ | Additive operator (also used for String concatenation) |
- | Subtraction operator |
* | Multiplication operator |
/ | Division operator |
% | Remainder operator |
The following program, ArithmeticDemo, tests the arithmetic operators.
class ArithmeticDemo {
public static void main (String[] args) {
int result = 1 + 2;
// result is now 3
System.out.println("1 + 2 = " + result);
int original_result = result;
result = result - 1;
// result is now 2
System.out.println(original_result + " - 1 = " + result);
original_result = result;
result = result * 2;
// result is now 4
System.out.println(original_result + " * 2 = " + result);
original_result = result;
result = result / 2;
// result is now 2
System.out.println(original_result + " / 2 = " + result);
original_result = result;
result = result + 8;
// result is now 10
System.out.println(original_result + " + 8 = " + result);
original_result = result;
result = result % 7;
// result is now 3
System.out.println(original_result + " % 7 = " + result);
}
}
This program prints the following:
1 + 2 = 3
3 - 1 = 2
2 * 2 = 4
4 / 2 = 2
2 + 8 = 10
10 % 7 = 3
You can also combine the arithmetic operators with the simple assignment operator to create compound assignments.
For example, x+=1; and x=x+1; both increment the value of x by 1.
The + operator can also be used for concatenating (joining) two strings together, as shown in the following ConcatDemo program:
class ConcatDemo {
public static void main(String[] args){
String firstString = "This is";
String secondString = " a concatenated string.";
String thirdString = firstString+secondString;
System.out.println(thirdString);
}
}
By the end of this program, the variable thirdString contains "This is a concatenated string.", which gets printed to standard output.
The unary operators require only one operand; they perform various operations such as incrementing/decrementing a value by one, negating an expression, or inverting the value of a boolean.
| Operator | Description |
|---|---|
+ | Unary plus operator; indicates positive value (numbers are positive without this, however) |
- | Unary minus operator; negates an expression |
++ | Increment operator; increments a value by 1 |
-- | Decrement operator; decrements a value by 1 |
! | Logical complement operator; inverts the value of a boolean |
The following program, UnaryDemo, tests the unary operators:
class UnaryDemo {
public static void main(String[] args) {
int result = +1;
// result is now 1
System.out.println(result);
result--;
// result is now 0
System.out.println(result);
result++;
// result is now 1
System.out.println(result);
result = -result;
// result is now -1
System.out.println(result);
boolean success = false;
// false
System.out.println(success);
// true
System.out.println(!success);
}
}
The increment/decrement operators can be applied before (prefix) or after (postfix) the operand.
The code result++; and ++result; will both end in result being incremented by one.
The only difference is that the prefix version (++result) evaluates to the incremented value, whereas the postfix version (result++) evaluates to the original value.
If you are just performing a simple increment/decrement, it doesn't really matter which version you choose.
But if you use this operator in part of a larger expression, the one that you choose may make a significant difference.
The following program, PrePostDemo, illustrates the prefix/postfix unary increment operator:
class PrePostDemo {
public static void main(String[] args){
int i = 3;
i++;
// prints 4
System.out.println(i);
++i;
// prints 5
System.out.println(i);
// prints 6
System.out.println(++i);
// prints 6
System.out.println(i++);
// prints 7
System.out.println(i);
}
}