org.metawidget.util.simple.ObjectUtils Maven / Gradle / Ivy
// Metawidget
//
// This file is dual licensed under both the LGPL
// (http://www.gnu.org/licenses/lgpl-2.1.html) and the EPL
// (http://www.eclipse.org/org/documents/epl-v10.php). As a
// recipient of Metawidget, you may choose to receive it under either
// the LGPL or the EPL.
//
// Commercial licenses are also available. See http://metawidget.org
// for details.
package org.metawidget.util.simple;
/**
* Utilities for working with Objects.
*
* @author Richard Kennard
*/
public final class ObjectUtils {
//
// Public statics
//
/**
* Compares the classes of the given Objects and returns true if they are identical. This check
* is typically used at the start of an equals implementation.
*
* @return true if object1 is the same class (exact same, not just assignable subclass) as
* object2. False otherwise.
*/
public static boolean nullSafeClassEquals( Object object1, Object object2 ) {
if ( object1 == null || object2 == null ) {
return false;
}
if ( object1.getClass() != object2.getClass() ) {
return false;
}
return true;
}
/**
* @return 0 if toHash is null, otherwise returns toHash.hashCode()
*/
public static int nullSafeHashCode( Object toHash ) {
if ( toHash == null ) {
return 0;
}
// Array.hashCode is broken by default
if ( toHash.getClass().isArray() ) {
return deepHashCode( (Object[]) toHash );
}
return toHash.hashCode();
}
/**
* Performs an equals() check on two Objects, either (or both) of which may be null.
*
* This method returns true if both Objects are null. Whether, strictly speaking,
* null == null is debatable, but this approach is useful for comparing two parent Objects who
* have both left certain properties as null. Generally we want those two parent Objects to be
* considered equal.
*
* @return true if both object1 and object2 are null, false if one is null and the other is not,
* otherwise returns object1.equals( object2 )
*/
public static boolean nullSafeEquals( Object object1, Object object2 ) {
if ( object1 == null ) {
return object2 == null;
}
// Array.equals is broken by default
if ( object1.getClass().isArray() ) {
if ( object2 == null || !object2.getClass().isArray() ) {
return false;
}
return deepEquals( (Object[]) object1, (Object[]) object2 );
}
return object1.equals( object2 );
}
/**
* @return 0 if both object1 and object2 are null, -1 if object1 is null but object2 is not
* (sorts nulls to the top), 1 if object2 is null but object1 is not, otherwise returns
* object1.compareTo( object2 )
*/
public static int nullSafeCompareTo( Comparable object1, T object2 ) {
if ( object1 == null ) {
if ( object2 == null ) {
return 0;
}
return -1;
} else if ( object2 == null ) {
return 1;
}
return object1.compareTo( object2 );
}
//
// Private methods
//
/**
* Copied from Arrays.deepHashCode. Arrays.deepHashCode not supported
* by GWT 1.7.
*/
private static int deepHashCode( Object[] a ) {
if ( a == null ) {
return 0;
}
int result = 1;
for ( Object element : a ) {
int elementHash = 0;
if ( element instanceof Object[] ) {
elementHash = deepHashCode( (Object[]) element );
} else if ( element != null ) {
elementHash = element.hashCode();
}
result = 31 * result + elementHash;
}
return result;
}
/**
* Copied from Arrays.deepEquals. Arrays.deepEquals not supported by
* GWT 1.7.
*/
private static boolean deepEquals( Object[] a1, Object[] a2 ) {
if ( a1 == a2 ) {
return true;
}
if ( a1 == null || a2 == null ) {
return false;
}
int length = a1.length;
if ( a2.length != length ) {
return false;
}
for ( int i = 0; i < length; i++ ) {
Object e1 = a1[i];
Object e2 = a2[i];
if ( e1 == e2 ) {
continue;
}
if ( e1 == null ) {
return false;
}
// Figure out whether the two elements are equal
boolean eq;
if ( e1 instanceof Object[] && e2 instanceof Object[] ) {
eq = deepEquals( (Object[]) e1, (Object[]) e2 );
} else {
eq = e1.equals( e2 );
}
if ( !eq ) {
return false;
}
}
return true;
}
//
// Private constructor
//
private ObjectUtils() {
// Can never be called
}
}