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package com.sun.appserv.management.util.misc;
import java.util.List;
import java.util.ArrayList;
import java.util.AbstractList;
import java.lang.reflect.Array;
import com.sun.appserv.management.util.stringifier.ArrayStringifier;
/**
A circular list implementation
*/
public final class CircularList<T> extends AbstractList<T>
{
private final T[] mObjects;
private int mNumItems;
private int mFirst;
private OverflowHandler mOverflowHandler;
public
CircularList( Class<T> theClass, final int size )
{
if ( size == 0 )
{
throw new IllegalArgumentException( "list must have at least one item" );
}
mObjects = ArrayUtil.newArray( theClass, size );
mFirst = 0;
mNumItems = 0;
mOverflowHandler = null;
}
public interface OverflowHandler
{
void handleBufferOverflow( Object o );
}
public void
setOverflowHandler( final OverflowHandler handler )
{
mOverflowHandler = handler;
}
public OverflowHandler
getOverflowHandler( )
{
return( mOverflowHandler );
}
public final int
size()
{
return( mNumItems );
}
public final int
capacity()
{
return( mObjects.length );
}
public final void
clear()
{
for( int i = 0; i < size(); ++i )
{
set( i, null );
}
mNumItems = 0;
++modCount;
}
private final int
getPhysicalIndex( final int logicalIndex )
{
return( (mFirst + logicalIndex) % capacity() );
}
public final T
get( final int i)
{
checkInBounds( i );
return( mObjects[ getPhysicalIndex( i ) ] );
}
public final T
set(
final int i,
final T item)
{
checkInBounds( i );
final int physicalIndex = getPhysicalIndex( i );
final T oldItem = mObjects[ physicalIndex ];
mObjects[ physicalIndex ] = item;
return( oldItem );
}
protected void
discardedObject( final T o )
{
if ( mOverflowHandler != null )
{
mOverflowHandler.handleBufferOverflow( o );
}
}
private final void
store(
final int logicalIndex,
final T item )
{
mObjects[ getPhysicalIndex( logicalIndex ) ] = item;
}
public final boolean
add( final T item )
{
final int capacity = capacity();
assert( mFirst < capacity );
// if we're full before adding, then we'll be overwriting
// the first item.
if ( size() == capacity )
{
final T overwrittenObject = get( 0 );
// first item will be overwritten; next one is first (oldest)
mFirst = (mFirst + 1) % capacity;
store( capacity - 1, item );
discardedObject( overwrittenObject );
}
else
{
store( mNumItems, item );
++mNumItems;
}
++modCount;
return( true );
}
/**
May be added to the end only.
*/
public final void
add(
final int index,
final T item )
{
if ( index == mNumItems )
{
add( item );
}
else
{
throw new UnsupportedOperationException( "add not at end" );
}
}
public final T
remove( final int i)
{
T result = null;
if ( i == 0 )
{
result = removeFirst();
}
else if ( i == mNumItems - 1 )
{
result = removeLast();
}
else
{
throw new UnsupportedOperationException();
}
++modCount;
return( result );
}
private final void
checkInBounds( final int i )
{
if ( i < 0 || i >= mNumItems )
{
throw new IndexOutOfBoundsException( "" + i );
}
}
public final T
removeFirst()
{
checkInBounds( 0 );
final T result = get( 0 );
--mNumItems;
mFirst = (mFirst + 1) % capacity();
return( result );
}
public final T
removeLast()
{
checkInBounds( 0 );
final T result = get( mNumItems - 1 );
--mNumItems;
return( result );
}
public boolean
equals( final Object rhsIn )
{
boolean equal = false;
if ( rhsIn == this )
{
equal = true;
}
else if ( ! (rhsIn instanceof CircularList) )
{
equal = false;
}
else
{
final CircularList rhs = (CircularList)rhsIn;
equal = capacity() == rhs.capacity() &&
size() == rhs.size();
if ( equal )
{
final int size = size();
for( int i = 0; i < size(); ++i )
{
if ( ! CompareUtil.objectsEqual( get( i ), rhs.get( i ) ) )
{
equal = false;
break;
}
}
}
}
return( equal );
}
public String
toString()
{
return( ArrayStringifier.stringify( toArray( ), ", " ) );
}
}
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