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The AP Java Subset. Topics. A Topics. Primitive Types. int double boolean. Operators. +, -, *, /, % ++, -- = +=, -=, *=, /=, %= ==, !=, , = &&, ||, !. Numeric Casts. (int) (double). String Concatenation. + - PowerPoint PPT Presentation
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The AP Java Subset
Topics
A Topics
Primitive Types
int double boolean
Operators
+, -, *, /, % ++, -- = +=, -=, *=, /=, %= ==, !=, <, >, <=, >= &&, ||, !
Numeric Casts
(int) (double)
String Concatenation
+ will convert numbers to strings and invoke
the toString() method on objects
Escape Sequences
\\ \” \n
Input & Output
INPUT IS NOT TESTED Output is restricted to System.out.print and
println Formatting output is not tested
Arrays
One-dimensional Arrays of primitive types & of objects Initialization of named arrays:
– int[] array = {1, 3, 6, 9};
Control Structures
if if/else while for return (do/while, switch, continue, break – not
tested)
Method Overloading
Understand signature of method Depends on number, types & order of
parameters Does not depend on return type of method
Classes
Construct objects with new operator Supply constructor parameters Invoke accessor & modifier methods Modify existing classes Design own classes
Visibility
All classes will be public All instance variable will be private Methods, constructors and constants are
either public or private NO protected
Comments
// single line comments /* */ block comments No Javadoc comments
Final & Static
final keyword is used for final block scope constants
static final class scope constants static methods static final variables NO – final parameters, final methods, final
classes, static variables
null & this
null reference is in the Java subset this is restricted to passing an implicit
parameter in its entirety to another method (obj.method(this))
Descriptions such as “the implicit parameter this”
Super
Use to invoke superclass constructor– ex: super(args);
Or to invoke superclass method– ex: super.method(args);
Constructors
Be able to implement Initialize all instance variables Don’t need to know default rules
Extend & Implement
extend classes implement interfaces Know inheritance!!!
Read and Understand
Be able to read definitions of interfaces and abstract classes
Understand that the abstract methods need to be redefined for non-abstract classes
Write interfaces or class declarations when given a general description of the interface or class
Equals
Know when to use == or .equals Objects: equals Identity: ==
Subclass to Superclass
No casting is needed to convert from a subclass to a superclass
Do need to know class casts:– ArrayList xx = new ArrayList();– yy = (yyclass)xx.get(i);
Packages
import statement import package.subpackage.class;
Exceptions
NullPointerException ArrayIndexOutOfBoundsException ArithmeticException ClassCastException IllegalArgumentException
Standard Library Methods
java.lang.Object– equals– toString
java.lang.Comparable– compareTo
java.lang.Integer– Integer(int value) //constructor– intValue– equals– toString– compareTo
Standard Library Methods (cont’d)
java.lang.Double– Double(double value) //constructor– doubleValue– equals– toString– compareTo
java.lang.String– compareTo– equals– length– substring– indexOf
Standard Library Methods (cont’d)
java.lang.Math– abs (for int and double)– pow– sqrt
java.util.Random– nextInt– nextDouble
Standard Library Methods (cont’d)
java.util.ArrayList– size– add– get– set– remove
AB Topics
Two-dimensional Arrays
Ragged arrays are not tested– int [][] x = new int[3][];
Don’t need to know int[3][3] is an array of arrays
Know that x[0].length is the number of columns in a rectangular two-dimensional array named x
Abstract Classes
AB students are expected to design own interfaces and abstract classes
Throwing Unchecked Exceptions
IllegalStateException NoSuchElementException
Standard Library Methods
java.lang.Object– equals– toString– hashCode
java.lang.Comparable– compareTo
java.lang.Integer– Integer(int value) //constructor– intValue– equals– toString– compareTo
Standard Library Methods (cont’d)
java.lang.Double– Double(double value) //constructor– doubleValue– equals– toString– compareTo
java.lang.String– compareTo– equals– length– substring– indexOf
Standard Library Methods (cont’d)
java.lang.Math– abs (for int and double)– pow– sqrt
java.util.Random– nextInt– nextDouble
Standard Library Methods (cont’d)
java.util.List– add– size– get– set– iterator– listIterator
java.util.ArrayList– All List methods– add– remove
Standard Library Methods (cont’d)
java.util.LinkedList– addFirst– addLast– getFirst– getLast– removeFirst– removeLast
Standard Library Methods (cont’d)
java.util.Set– add– contains– remove– size– iterator
java.util.HashSet java.util.TreeSet
Standard Library Methods (cont’d)
java.util.Map– put– get– remove– containsKey– size– keySet
java.util.HashMap java.util.TreeMap
Standard Library Methods (cont’d)
java.util.Iterator– hasNext– next– remove
Java.util.ListIterator– add– set
Online resources
Acorn online Java API