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Bart van Kuik Application Developer Oracle Corporation

Bart van Kuik Application Developer Oracle Corporation. Java 1.5 New Language Features. Java 1.5: Tiger. Minder "standaard" code door syntax veranderingen Geen nieuwe keywords i.v.m. oude code, behalve enum. Toevoegingen Aan Syntax. Generics Enhanced for loop Autoboxing/unboxing

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Bart van Kuik Application Developer Oracle Corporation

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  1. Bart van KuikApplication Developer Oracle Corporation

  2. Java 1.5 New Language Features

  3. Java 1.5: Tiger • Minder "standaard" code door syntax veranderingen • Geen nieuwe keywords i.v.m. oude code, behalve enum

  4. Toevoegingen Aan Syntax • Generics • Enhanced for loop • Autoboxing/unboxing • Typesafe enums • Static Imports • Varargs • Metadata

  5. Generics • Ook wel 'parameterized types' List<String> lijstMetNamen = new ArrayList<String>(); // 1.4: runtime error / 1.5: compiler error lijstMetNamen.add(new Integer(1)); • Feature: covariant return types

  6. Enhanced for loop List list = new List(); for(Iterator i = list.iterator(); i.hasNext();) { String s = (String) i.next(); System.out.println("String: " + s); } List<String> list = new List(); for (String s : list) { System.out.println("String: " + s); } String naam = "Harry"; for (char c : naam.toCharArray()) {}

  7. Autoboxing/unboxing • public static void Koe.melken(Integer liter);public static void Aap.gooien(int Aantal); • Automatisch primitive van/naar reference:int i = 4;Koe.melken(new Integer(i)); // 1.4Koe.melken(i); // 1.5Object obj = new Integer(3);Aap.gooien(((Integer)obj).intValue()); // 1.4Aap.gooien((Integer)obj); // 1.5 • null geeft een NullPointerException

  8. Typesafe enums • Diverse nadelen:class Kaart { static final int HARTEN = 0; static final int KLAVEREN = 1; static final int RUITEN = 2; static final int SCHOPPEN = 3;} • Nieuw:public enum Kaart { harten, klaveren, ruiten, schoppen}

  9. Static Imports • Pre 1.5: veel tikwerk om constanten te gebruiken, bijvoorbeeld:ErrorConstants.XML_NOT_VALID • Nieuwe vorm van import-statement:import static com.elsevier.ew.ErrorConstants.*; • Zowel static methods als attributes

  10. Varargs • Variabel aantal argumenten aan methoden • printf("Waarde: %d", 15); • Compiler begrijpt de volgende syntaxpublic static int optellen(int args...) { int resultaat = 0; for(i = 0; i < args.length; i++) restultaat = resultaat + args[i];}

  11. Metadata • Nieuwste toevoeging • Aanwijzing voor precompilers, testtools, e.d. • C# attribute syntax: [xxx] • Java metadata syntax: @xxx@testpublic static int optellen(int... params) { // blah}

  12. Conclusie • Door JCP gelopen • Early access 2.2 is te bewonderen • Beta en Final release ergens in 2004 • Grote namen: Joshua Blog, Neil Gafter

  13. Q & Q U E S T I O N S A N S W E R S A

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