- Relational operators always result in a Boolean value( true or false)
- There are six relational operators >, >=, <, <=, == and != The last two (== and !=) are sometimes referred to as equality operators.
- When comparing characters, java uses the Unicode value of the character as the numerical value.
- Equality operators:
- There are two equality operators. == and !=
- Four types of things can be tested: Numbers, Characters, and Booleans and Reference variables.
- When comparing reference variables. == Returns true if both references refer to same object.
- Instanceof is for reference variables only, and checks for weather the object is of particular type.
- The instance of operator can be used only to test objects (or null) against class types that are in the same hierarchy.
- For interfaces, an object passes the Instanceof test if any of its subclasses implement the interface on the right side of the Instanceof operator.
- There are four primary math operators: add, subtract, multiply, and divide.
- The remainder operator (%), returns the remainder of division.
- Expressions are evaluated from left to right, unless you add parenthesis, or unless same operators in the expression have higher precedence than others.
- The *, /, and % have higher precedence than + and -.
String concatenation Operators:
- If either operand is a String the + operator concatenates the operands.
- If both operands are numeric the + operator adds the operands.
Increment / Decrement operators:
- Prefix operators (++ and –) run before the value is used in expression.
- Postfix operators (++ and –) run after the value is used in the expression.
- If any expression, both operands fully evaluated before the operator is applied.
- Variables marked as final cannot be incremented or decremented.
Ternary (Conditional operator):
- Returns one of the two values based on the Boolean expression is true of false.
- Returns the value after the ? if the expression is true.
- Returns the value after the : if the expression is false.
- The exam covers six “logical” operators &, |, ^, !, &&, and ||.
- Logical operators work with two operands (except for !) that must resolve Boolean values.
- The && and & operators returns true if both operands are true.
- The || and | operator returns true if either or both operands are true.
- && and || operators are known as short circuit operators.
- The && operator dose not evaluate the right operand if the left operand is false.
- The || operator doesn’t evaluate the right operand if the left operand is true.
- The & and | operators always evaluate both operands.
- The ^ operator (called logical XOR), returns true if exactly one operand is true.
- The ! Operator (called the inversion operator), returns the opposite value of both Boolean operand it precedes.