Generic classes Declaration Use Annotations 54 Generic classes - - PowerPoint PPT Presentation

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Generic classes Declaration Use Annotations 54 Generic classes - - PowerPoint PPT Presentation

Jan 26, 2024 43 likes •279 views

Generic classes Declaration Use Annotations 54 Generic classes Declaration add generic types between angle brackets: public class MyStack < E,F >{ E item; } 55 Generic Classes Use MyStack<Integer> ms= new

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SLIDE 1

Generic classes

  • Declaration
  • Use
  • Annotations

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SLIDE 2

Generic classes Declaration

  • add generic types between angle brackets:

public class MyStack<E,F>{ E item; }

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SLIDE 3

Generic Classes Use

MyStack<Integer> ms= new MyStack<Integer>();

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SLIDE 4

Generic Classes Annotations

  • public int count(MyClass<?> mc){...}
  • public int count(MyClass<? extends String>

mc){...}

  • public int count(MyClass<? extends String &

Countable> mc){...}

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SLIDE 5

Why not subtype generics

MyStack<Integer> myStack=new MyStack<Integer>(); public static void add(Stack<Object> st, Object o){ st.add(o); }

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SLIDE 6

Example: MySmallStack

public void add(E value){ Element<E> e; e= new Element<E>(value); e.next=this.first; this.first=e; } ... MySmallStack<Integer> myStack = new MySmallStack<Integer>(); myStack.add(1);

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SLIDE 7

Nested Classes

  • Classes that are declared in a file, along

another one

  • If outside a class: static
  • If inside, it depends... they can be inner

classes

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SLIDE 8

Inner Classes

  • A particular type of nested classes
  • Anonymous
  • Method-scope
  • Class scope

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SLIDE 9

Anonymous Inner Classes

  • Declared at instanciation

public void wave(){ Object o = new Object(){ public Object clone(){ return this; } }; ... }

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SLIDE 10

Method Inner classes

  • declared in a method
  • visible only in the method

// method declaration public void wave(){ class Hello2 extends HelloWorld{ }; ... }

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SLIDE 11

Class Inner Classes

  • Declared in the class
  • visibility decides on access control outside
  • f the class

public class HelloWorld extends Object{ class Hello2 extends HelloWorld{ }; // method declaration public void wave(){ ... } } ... HelloWorld.Hello2 h=new HelloWorld.Hello2();

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SLIDE 12

Some interesting classes

  • Object
  • String
  • System
  • Vector

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SLIDE 13

Object

  • See API

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SLIDE 14

String

  • See API

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SLIDE 15

System

  • See APIs

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SLIDE 16

Vector

  • See APIs

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SLIDE 17

Java Basics Part 3 - Exceptions

Manuel Oriol, April 13th, 2006

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SLIDE 18

Throwable

  • The Throwable interface is meant to

represent computational events that can interrupt the current computation

  • Computation can occur after the event is

handled

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SLIDE 19

Exception

  • Exceptions represent events that are meant

to be treated.

  • Whenever a method may trigger an

exception, it is required that it declares so (modulo conformance). Except for RuntimeExceptions.

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SLIDE 20

Runtime Exceptions

AnnotationTypeMismatchException, ArithmeticException, ArrayStoreException, BufferOverflowException, BufferUnderflowException, CannotRedoException, CannotUndoException, ClassCastException, CMMException, ConcurrentModificationException, DOMException, EmptyStackException, EnumConstantNotPresentException, EventException, IllegalArgumentException, IllegalMonitorStateException, IllegalPathStateException, IllegalStateException, ImagingOpException, IncompleteAnnotationException, IndexOutOfBoundsException, JMRuntimeException, LSException, MalformedParameterizedTypeException, MissingResourceException, NegativeArraySizeException, NoSuchElementException, NullPointerException, ProfileDataException, ProviderException, RasterFormatException, RejectedExecutionException, SecurityException, SystemException, TypeNotPresentException, UndeclaredThrowableException, UnmodifiableSetException, UnsupportedOperationException ...

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SLIDE 21

Error

  • Meant to represent an unrecoverable error
  • Can be recovered still...
  • Example: AnnotationFormatError, AssertionError,

AWTError, CoderMalfunctionError, FactoryConfigurationError, LinkageError, ThreadDeath, TransformerFactoryConfigurationError, VirtualMachineError

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SLIDE 22

Throw, throws

  • it is possible to throw an exception manually

by using: throw an_exception;

  • methods that may fail due to an exception

(non-runtime) have to indicate it: public void m() throws MyException{...}

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SLIDE 23

try...catch... finally

try{ ... } catch (MyException1 e){...} catch (MyException2 e){...} ... finally{...}

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