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Comprehensive Overview of Java Primitive Types and Basic Concepts

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This guide provides a thorough overview of fundamental Java concepts, focusing on primitive types such as int, double, and boolean, along with operators, control structures, and method overloading. It explains numeric casts, string concatenation, escape sequences, and input/output handling. Readers will learn about class design, constructors, visibility modifiers, and the importance of exception handling. The document also covers key standard library methods and array management, ensuring a solid foundational understanding for Java programming.

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Comprehensive Overview of Java Primitive Types and Basic Concepts

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  1. The AP Java Subset Topics

  2. A Topics

  3. Primitive Types • int • double • boolean

  4. Operators • +, -, *, /, % • ++, -- • = • +=, -=, *=, /=, %= • ==, !=, <, >, <=, >= • &&, ||, !

  5. Numeric Casts • (int) • (double)

  6. String Concatenation • + • will convert numbers to strings and invoke the toString() method on objects

  7. Escape Sequences • \\ • \” • \n

  8. Input & Output • INPUT IS NOT TESTED • Output is restricted to System.out.print and println • Formatting output is not tested

  9. Arrays • One-dimensional • Arrays of primitive types & of objects • Initialization of named arrays: • int[] array = {1, 3, 6, 9};

  10. Control Structures • if • if/else • while • for • return • (do/while, switch, continue, break – not tested)

  11. Method Overloading • Understand signature of method • Depends on number, types & order of parameters • Does not depend on return type of method

  12. Classes • Construct objects with new operator • Supply constructor parameters • Invoke accessor & modifier methods • Modify existing classes • Design own classes

  13. Visibility • All classes will be public • All instance variable will be private • Methods, constructors and constants are either public or private • NO protected

  14. Comments • // single line comments • /* */ block comments • No Javadoc comments

  15. 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

  16. 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”

  17. Super • Use to invoke superclass constructor • ex: super(args); • Or to invoke superclass method • ex: super.method(args);

  18. Constructors • Be able to implement • Initialize all instance variables • Don’t need to know default rules

  19. Extend & Implement • extend classes • implement interfaces • Know inheritance!!!

  20. 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

  21. Equals • Know when to use == or .equals • Objects: equals • Identity: ==

  22. 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);

  23. Packages • import statement • import package.subpackage.class;

  24. Exceptions • NullPointerException • ArrayIndexOutOfBoundsException • ArithmeticException • ClassCastException • IllegalArgumentException

  25. Standard Library Methods • java.lang.Object • equals • toString • java.lang.Comparable • compareTo • java.lang.Integer • Integer(int value) //constructor • intValue • equals • toString • compareTo

  26. Standard Library Methods (cont’d) • java.lang.Double • Double(double value) //constructor • doubleValue • equals • toString • compareTo • java.lang.String • compareTo • equals • length • substring • indexOf

  27. Standard Library Methods (cont’d) • java.lang.Math • abs (for int and double) • pow • sqrt • java.util.Random • nextInt • nextDouble

  28. Standard Library Methods (cont’d) • java.util.ArrayList • size • add • get • set • remove

  29. AB Topics

  30. 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

  31. Abstract Classes • AB students are expected to design own interfaces and abstract classes

  32. Throwing Unchecked Exceptions • IllegalStateException • NoSuchElementException

  33. Standard Library Methods • java.lang.Object • equals • toString • hashCode • java.lang.Comparable • compareTo • java.lang.Integer • Integer(int value) //constructor • intValue • equals • toString • compareTo

  34. Standard Library Methods (cont’d) • java.lang.Double • Double(double value) //constructor • doubleValue • equals • toString • compareTo • java.lang.String • compareTo • equals • length • substring • indexOf

  35. Standard Library Methods (cont’d) • java.lang.Math • abs (for int and double) • pow • sqrt • java.util.Random • nextInt • nextDouble

  36. Standard Library Methods (cont’d) • java.util.List • add • size • get • set • iterator • listIterator • java.util.ArrayList • All List methods • add • remove

  37. Standard Library Methods (cont’d) • java.util.LinkedList • addFirst • addLast • getFirst • getLast • removeFirst • removeLast

  38. Standard Library Methods (cont’d) • java.util.Set • add • contains • remove • size • iterator • java.util.HashSet • java.util.TreeSet

  39. Standard Library Methods (cont’d) • java.util.Map • put • get • remove • containsKey • size • keySet • java.util.HashMap • java.util.TreeMap

  40. Standard Library Methods (cont’d) • java.util.Iterator • hasNext • next • remove • Java.util.ListIterator • add • set

  41. Online resources • Acorn online • Java API

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