# Class: com.pnfsoftware.jeb.util.collect.CollectionUtil Convenience methods for Java [collections](Collection), in particular, [lists](List). ## Static Method: addNonNulls - parameter: `dst`, type: `java.util.Collection` - parameter: `src`, type: `java.util.Collection` - return type: `java.util.Collection` Description: Add all non\-null source elements to a destination collection. parameter: T: element type parameter: dst: destination collection parameter: src: optional source collection return: the destination collection ## Static Method: addNonNulls - parameter: `dst`, type: `java.util.Collection` - parameter: `elts`, type: `T[]` - return type: `java.util.Collection` Description: Add all non\-null elements to a destination collection. parameter: T: element type parameter: dst: destination collection parameter: elts: optional elements return: the destination collection ## Static Method: binarySearch - parameter: `list`, type: `java.util.List` - parameter: `key`, type: `K` - parameter: `extractor`, type: `com.pnfsoftware.jeb.util.collect.IExtractor` - return type: `T` Description: Perform a binary search in an ordered list. parameter: T: element type parameter: K: key type parameter: list: a list of ordered items parameter: key: the ordering key for the items. parameter: extractor: key extractor return: the element, null if not found ## Static Method: binarySearchEx - parameter: `list`, type: `java.util.List` - parameter: `key`, type: `K` - parameter: `extractor`, type: `com.pnfsoftware.jeb.util.collect.IExtractor` - parameter: `cc`, type: `java.util.Comparator` - return type: `int` Description: Perform a binary search in an ordered list. parameter: T: element type parameter: K: key type parameter: list: a list of ordered items parameter: key: the ordering key for the items. parameter: extractor: key extractor parameter: cc: optional custom comparator for the keys return: the zero\+ index of the found element; else, the negative insertion index of the ghost element ## Static Method: compare - parameter: `c1`, type: `java.util.Collection` - parameter: `c2`, type: `java.util.Collection` - parameter: `sorted`, type: `boolean` - return type: `boolean` Description: Compare two collections using element equality. parameter: T: element type parameter: c1: first collection parameter: c2: second collection parameter: sorted: true if iteration order must be considered return: true if the collections contain the same elements ## Static Method: compareByReference - parameter: `c1`, type: `java.util.Collection` - parameter: `c2`, type: `java.util.Collection` - parameter: `sorted`, type: `boolean` - return type: `boolean` Description: Compare two collections using reference identity for elements. parameter: T: element type parameter: c1: first collection parameter: c2: second collection parameter: sorted: true if iteration order must be considered return: true if the collections contain the same references ## Static Method: contains - parameter: `c`, type: `java.util.Collection` - parameter: `v`, type: `java.lang.Object` - return type: `boolean` Description: Safely check if an object is present within a collection. parameter: c: collection, potentially null parameter: v: object, potentially null return: true IFF the object is contained in the collection ## Static Method: containsNonNull - parameter: `c`, type: `java.lang.Iterable` - return type: `boolean` Description: Determine if the given iterable contains one or more non\-null elements. parameter: c: iterable to inspect return: true if at least one element is not null ## Static Method: containsNull - parameter: `c`, type: `java.lang.Iterable` - return type: `boolean` Description: Determine if the given iterable contains one or more null elements. parameter: c: iterable to inspect return: true if at least one element is null ## Static Method: containsReference - parameter: `c`, type: `java.util.Collection` - parameter: `o`, type: `T` - return type: `boolean` Description: Determine if the collection contains the object reference \(differs from [Collection#contains(Object)](Collection#contains(Object)) by checking reference equality ` == ` instead of [Object#equals(Object)](Object#equals(Object)) equality\) parameter: T: element type parameter: c: collection to loop into parameter: o: element whose presence in this collection is to be tested return: true if the collection contains the specified element ## Static Method: count - parameter: `coll`, type: `java.util.Collection` - parameter: `item`, type: `T` - return type: `int` Description: Count elements using [Object#equals(Object)](Object#equals(Object)). parameter: T: element type parameter: coll: collection to inspect parameter: item: item to count return: number of equal elements ## Static Method: doubleCollectionIterable - parameter: `coll1`, type: `java.util.Collection` - parameter: `coll2`, type: `java.util.Collection` - return type: `java.lang.Iterable` Description: Create a generator that will iterate over two collections, starting with the first one, then the second one. This method is convenient to iterate over two collections without having to create an intermediate list holding the elements. parameter: T: element type parameter: coll1: first collection parameter: coll2: second collection return: an iterable ## Static Method: first - parameter: `coll`, type: `java.util.Collection` - return type: `T` Description: Retrieve the first item of a [Collection](Collection). This method is safe and returns null if the collection is null or empty. parameter: T: element type parameter: coll: a collection return: the first item or null if collection is null or empty ## Static Method: hasIntersection - parameter: `c1`, type: `java.util.Collection` - parameter: `c2`, type: `java.util.Collection` - return type: `boolean` Description: Determine whether two collections share at least one element. parameter: T: element type parameter: c1: first collection parameter: c2: second collection return: true if both collections contain at least one equal element ## Static Method: identityCount - parameter: `coll`, type: `java.util.Collection` - parameter: `item`, type: `T` - return type: `int` Description: Count elements using `==`. parameter: T: element type parameter: coll: collection to inspect parameter: item: item to count return: number of identical elements ## Static Method: intersect - parameter: `c1`, type: `java.util.Collection` - parameter: `c2`, type: `java.util.Collection` - return type: `java.util.Set` Description: Return the intersection of 2 collections \(order of collection parameters does not matter\). parameter: T: element type parameter: c1: first collection parameter: c2: second collection return: a set of intersection ## Static Method: last - parameter: `coll`, type: `java.util.Collection` - return type: `T` Description: Retrieve the last item of a [Collection](Collection). This method is safe and returns null if the collection is null or empty. parameter: T: element type parameter: coll: a collection return: the last item or null if collection is null or empty