Java6学习笔记——ArrayList类的学习

在编程中经常会碰到需要动态操作的数组，比如在运行时增加和删除数组元素，而且有时在编译时又不想确定数组大小希望它可以动态伸缩，在Java中解决这一问题的方法是使用java.util包中的ArrayList类，该类提供了许多的方法可以实现数组的动态操控。如果试图给ArrayList类添加走出容量允许范围的对象数，它会自动增大，新增的内在区域是当前容量两倍的元素，并重新定位这些元素。

简而言之，ArrayList类是List的可变数组的实现。

import java.util.List;

import java.util.ArrayList;

import java.util.Collection;

import java.util.Iterator;


public class CollectionTest 

{

   private static final String[] colors = 

      { "MAGENTA", "RED", "WHITE", "BLUE", "CYAN" };

   private static final String[] removeColors = 

      { "RED", "WHITE", "BLUE" };


   // create ArrayList, add Colors to it and manipulate it

   public CollectionTest()

   {

      List< String > list = new ArrayList< String >();      

      List< String > removeList = new ArrayList< String >();


      // add elements in colors array to list

      for ( String color : colors )

         list.add( color );       


      // add elements in removeColors to removeList

      for ( String color : removeColors )

         removeList.add( color ); 


      System.out.println( "ArrayList: " );


      // output list contents

      for ( int count = 0; count < list.size(); count++ )

         System.out.printf( "%s ", list.get( count ) );


      // remove colors contained in removeList

      removeColors( list, removeList );


      System.out.println( "\n\nArrayList after calling removeColors: " );


      // output list contents

      for ( String color : list )

         System.out.printf( "%s ", color );


      System.out.println();

   } // end CollectionTest constructor


   // remove colors specified in collection2 from collection1

   private void removeColors( 

      Collection< String > collection1, Collection< String > collection2 )

   {

      // get iterator

      Iterator< String > iterator = collection1.iterator(); 


      // loop while collection has items

      while ( iterator.hasNext() )         


         if ( collection2.contains( iterator.next() ) )

            iterator.remove(); // remove current Color

   } // end method removeColors


   public static void main( String args[] )

   {

      new CollectionTest();

   } // end main

} // end class CollectionTest


输出：


ArrayList:

MAGENTA RED WHITE BLUE CYAN


ArrayList after calling removeColors:

MAGENTA CYAN