gw.util.GosuCollectionUtil Maven / Gradle / Ivy
/*
* Copyright 2014 Guidewire Software, Inc.
*/
package gw.util;
import java.util.Map;
import java.util.HashMap;
import java.util.Collections;
import java.util.List;
import java.util.ArrayList;
import java.util.Iterator;
public class GosuCollectionUtil
{
//----------------------------------------------------------------------------------------
// Collection utilities
//----------------------------------------------------------------------------------------
/**
* Returns a compacted and locked map representing the map passed in. This method can freely change the
* implementation type of the map. I.e. it can return an emptyMap, singletonMap, or even a completely different map implementation.
*/
public static Map compactAndLockHashMap( HashMap map )
{
if( map == null || map.isEmpty() )
{
return Collections.emptyMap();
}
if( map.size() == 1 )
{
Map.Entry stEntry = map.entrySet().iterator().next();
return Collections.singletonMap( stEntry.getKey(), stEntry.getValue() );
}
Map newMap = new HashMap( map.size(), 1 );
newMap.putAll( map );
return Collections.unmodifiableMap( newMap );
}
/**
* Returns a compacted and locked list representing the list passed in.
*/
public static List compactAndLockList( List list )
{
if( list == null || list.isEmpty() )
{
return Collections.emptyList();
}
if( list.size() == 1 )
{
return Collections.singletonList( list.get( 0 ) );
}
if( list instanceof ArrayList )
{
((ArrayList)list).trimToSize();
}
return Collections.unmodifiableList( list );
}
/**
* {@link String#startsWith(String)} for Lists.
*
* @return true iff list is at least as big as prefix, and if the first prefix.size() elements
* are element-wise equal to the elements of prefix.
*/
public static boolean startsWith( List list, List prefix )
{
if( list.size() < prefix.size() )
{
return false;
}
Iterator listIter = list.iterator();
for( Object prefixElement : prefix )
{
boolean b = listIter.hasNext();
assert b :
"list claims to have at least as many elements as prefix, but its iterator is exhausted first";
if( !GosuObjectUtil.equals( prefixElement, listIter.next() ) )
{
return false;
}
}
return true;
}
}