Friday, February 4, 2011

Quick Review - Chapters 22 to 26

Below is a review of the most important points that were covered in the previous Chapters

Relational Operators
* 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, booleans, and reference variables.
* When comparing reference variables, == returns true only if both references refer to the same object.

instanceof Operator
* instanceof is for reference variables only, and checks for whether the object is of a particular type.
* The instanceof operator can be used only to test objects (or null) against class types that are in the same class hierarchy.
* For interfaces, an object passes the instanceof test if any of its superclasses implement the interface on the right side of the instanceof operator.

Arithmetic Operators
* There are four primary math operators: add, subtract, multiply, and divide.
* The remainder operator (%), returns the remainder of a division.
* Expressions are evaluated from left to right, unless you add parentheses, or unless some operators in the expression have higher precedence than others.
* The *, /, and % operators have higher precedence than + and -.

String Concatenation Operator
* 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 the expression.
* Postfix operators (++ and --) run after the value is used in the expression.
* In any expression, both operands are fully evaluated before the operator is applied.
* Variables marked final cannot be incremented or decremented.

Ternary (Conditional Operator)
* Returns one of two values based on whether a boolean expression is true or false.
- Returns the value after the ? if the expression is true.
- Returns the value after the : if the expression is false.

Logical Operators
* The exam covers six “logical” operators: &, |, ^, !, &&, and ||.
* Logical operators work with two expressions (except for !) that must resolve to boolean values.
* The && and & operators return true only if both operands are true.
* The || and | operators return true if either or both operands are true.
* The && and || operators are known as short-circuit operators.
* The && operator does not evaluate the right operand if the left operand is false.
* The || does not evaluate the right operand if the left operand is true.
* The & and | operators always evaluate both operands.
* The ^ operator (called the “logical XOR”), returns true if exactly one operand is true.
* The ! operator (called the “inversion” operator), returns the opposite value of the boolean operand it precedes.


Previous Chapter: Chapter 26 - Logical Operators

Next Chapter: Self Test - Chapters 22 to 26

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