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Java in a Nutshell

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Java Syntax

13.3 Operators

Operators lists the operators of the Java language, along with their precedence, operand types, and associativity.

Table 13.3: Java Operators
Prec. Operator Operand Type(s) Assoc. Operation Performed
1 ++ arithmetic R pre-or-post increment (unary)
  -- arithmetic R pre-or-post decrement (unary)
  +, - arithmetic R unary plus, unary minus
  ~ integral R bitwise complement (unary)
  ! boolean R logical complement (unary)
  (type) any R cast
2 *, /, % arithmetic L multiplication, division, remainder
3 +, - arithmetic L addition, subtraction
  + string L string concatenation
4 << integral L left shift
  >> integral L right shift with sign extension
  >>> integral L right shift with zero extension
5 <, <= arithmetic L less than, less than or equal
  >, >= arithmetic L greater than, greater than or equal
  instanceof object, type L type comparison
6 == primitive L equal (have identical values)
  != primitive L not equal (have different values)
  == object L equal (refer to same object)
  != object L not equal (refer to different objects)
7 & integral L bitwise AND
  & boolean L boolean AND
8 ^ integral L bitwise XOR
  ^ boolean L boolean XOR
9 | integral L bitwise OR
  | boolean L boolean OR
10 && boolean L conditional AND
11 || boolean L conditional OR
12 ?: boolean, any, any R conditional (ternary) operator


variable, any R assignment

*=, /=, %=, +=, -=, <<=, >>=, >>>=, &=, ^=, |=

variable, any R assignment with operation

Operator precedence controls the order in which operations are performed. Consider the following example:

w = x + y * z;

The multiplication operator * has a higher precedence than the addition operator +, so the multiplication is performed before the addition. Furthermore, the assignment operator = has the lowest precedence of any operator, so the assignment is done after all the operations on the right-hand side are performed. Operators with the same precedence (like addition and subtraction) are performed in order according to their associativity (usually left-to-right). Operator precedence can be overridden with the explicit use of parentheses. For example:

w = (x + y) * z;

The associativity of an operator specifies the order that operations of the same precedence are performed in. In Table 13.3 a value of L specifies left-to-right associativity, and a value of R specifies right-to-left associativity. Left-to-right associativity means that operations are performed left-to-right. For example:

w = x + y + z;

is the same as:

w = ((x + y) + z);

because the addition operator has left-to-right associativity. On the other hand, the following expressions:

x = ~-~y;
q = a?b:c?d:e?f:g;

are equivalent to:

x = ~(-(~y));
q = a?b:(c?d:(e?f:g));

because the unary operators and the ternary conditional ?: operator have right-to-left associativity.

Java operators are basically identical to C operators, except for these differences:

  • The + operator applied to String values concatenates them. If only one operand of + is a String, the other one is converted to a string. The conversion is done automatically for primitive types and by calling the toString method of non-primitive types.

  • Java does not have the comma operator like C does. It does, however, simulate this operator in the limited context of the for loop initialization and increment expressions.

  • Since all Java integral types are signed, the >> operator always does a signed right shift, filling in high bits with the sign bit of the operand. The new >>> operator performs an unsigned right shift, filling in high bits of the shifted value with zero bits.

  • The & and | operators perform bitwise AND and OR operations on integral operands, and perform logical AND and OR operators on boolean operands. && and || also perform logical AND and OR on boolean operands, but do not evaluate the right-hand operand, if the result of the operation is fully determined by the left-hand operand.

  • The instanceof operator returns true if the object on the left-hand side is an instance of the class or implements the interface on the right-hand side. Otherwise it returns false. If the left-hand side is null, it returns false.

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