Final Exam Topics Review

• Printing to the console

• System.out.print() and System.out.println()
• Also used by PrintWriter objects

• Reading input from the keyboard

• Scanner class

• keyboard input: System.in
• File input: File object ← may throw an Exception

• methods to read input
• methods to peek at input (hasNextSOMETYPE())

• Declaring and initializing variables

• variableType variableName; ← declaration
• type could be a primitive, could be a provided class from a Java library, could be from a class that you’ve defined
• initialization

• literal: int x = 5;
• using constructor: String str = new String(“Hello”);
• from some method call: MyClass c = createNewMyClass();

• int[][] x = initalizeA2DArray(num);

• difference between primitive and reference types

• primitive types: int, double (numeric), char, boolean

• contain values

• reference types: reference variables contain reference to object; multiple reference variables can be references to the same object (be careful with the assignment operator!)

• Numeric operations

• numeric operators (+, -, …)
• augmented assignment operators (+=, …)
• increment(++), decrement(--)
• Math class methods

• static methods
• invoked Math.methodName() ← ClassName.methodName()

• e.g., Math.pow(2,4)

• rounding (& truncation)

• type casting

• Booleans

• logical operators (!, &&, ||, ^): operate on one or more booleans
• relational operators: operate on two or more non-boolean values = boolean expression

• conditionals

• if, if-else, if-else if-else
• nested if
• switch statements

• break keyword

• char, Character class methods ← static methods
• String class, String methods ← instance methods
• loops

• while, do-while
• for loops
• loop continuation conditions
• counter-controlled loops vs. sentinel-controlled loops
• pretest (for, while), posttest loops (do-while)
• common algorithms: summation, searching
• nested loops

while (!found) {

for (i = 0; i < 10; i++) {

for (j = 0; j < 5; j++) {

found = true

}

}        

                }

• methods

• writing a method header
• return values (make sure to include a return statement when a method returns a value)
• specifying, passing parameters, primitive vs. reference params
• overloading methods
• variable scope

• arrays

• declaring, initializing arrays
• iterating over the elements of an array
• copying arrays
• searching an array
• Example: OddArrayValues.java
• The Arrays class
• ArrayLists

• defining classes

• data fields
• methods, including constructor(s)
• static vs. instance (non-static)
• public/private/protected (abstract classes--protected can only be used in a subclass)
• this keyword
• instantiate a new object of a particular class
• Example: UsingCars.java

• Casting: CastingExample.java (uses the BankAccount and SavingsAccount classes)

For Wednesday:

• more inheritance and polymorphism
• abstract classes, interfaces
• exceptions
• file I/O
• …
• Examples

Wednesday

• inheritance & polymorphism

• extends keyword; superclass and subclass (extends the superclass)
• super keyword

• when invoking constructor in subclass, first must invoke (explicitly or implicitly: super()) a constructor for the superclass

• abstract class: cannot be instantiated (but can be used as datatypes); abstract methods are only implemented in subclasses
• overriding methods (redefining an inherited method)

• vs. overloading methods

• casting

• double d = 5.5;
• int i = (int)d;
• Examples: CastingExample.java, checkpoints for ch. 13
• instanceof operator

• Object class: equals(), toString() methods
• interfaces

• implements keyword
• Comparable<E> interface, compareTo() method
• Example: UsingCars.java

• Exceptions

• try-catch,
• checked vs. unchecked exceptions
• (re)throwing exceptions
• chained exceptions

• File I/O

• File class
• Reading from files: Scanner class
• Writing to files: PrintWriter class