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a-base is a library of basic (hence the name) classes, most notably immutable collection classes with copy-on-write operations
package com.ajjpj.abase.collection.immutable;
import com.ajjpj.abase.collection.ACollectionHelper;
import com.ajjpj.abase.collection.AEquality;
import com.ajjpj.abase.collection.AEqualsWrapper;
import com.ajjpj.abase.function.AFunction1;
import com.ajjpj.abase.function.APredicate;
import com.ajjpj.abase.function.APredicateNoThrow;
import com.ajjpj.abase.function.AStatement1;
import java.lang.reflect.Array;
import java.util.Collection;
import java.util.Iterator;
import java.util.Map;
/**
* This is an abstract convenience superclass for implementing ACollection implementations.
*
* It has two generic parameters. The first of these parameters is the element types, and the second parameter is the type
* of the concrete collection; it is used as a return type for some collection methods.
*
* This class provides default implementations for most of ACollection's methods, many of them based on ACollectionHelper
* calls. While these implementations work, it is up to the implementer to decide where a more specific implementation
* is called for to leverage internals of the actual collection class.
*
* There are three methods that form the foundation for these generic implementations:
*
* - size() returns the number of elements in the collection
* - iterator() returns an iterator over the collection's elements
* - createInternal() creates a new instance of the collection, containing a given list of elements
*
*
* The methods flatten(), flatMap() and map() are not implemented generically in this class
* because there is no way to provide the concrete collection class as their return type.
*
* The equals() and hashCode() implementations are based on the AEquality instance provided
* by equalityForEquals().
*
* @author arno
*/
public abstract class AbstractACollection> implements ACollection {
protected abstract C createInternal(Collection elements);
protected abstract AEquality equalityForEquals();
@Override public boolean isEmpty() {
return size() == 0;
}
@Override public boolean nonEmpty() {
return size() > 0;
}
@Override public void forEach(AStatement1 f) throws E { //TODO junit
for(T o: this) {
f.apply(o);
}
}
@Override public C filter(APredicate pred) throws E {
return createInternal(ACollectionHelper.filter(this, pred));
}
@Override public AMap groupBy(AFunction1 f) throws E {
final Map> raw = ACollectionHelper.groupBy(this, f);
AMap result = AHashMap.empty();
for(Map.Entry> entry: raw.entrySet()) {
result = result.updated(entry.getKey(), createInternal(entry.getValue()));
}
return result;
}
@Override public AMap groupBy(AFunction1 f, AEquality keyEquality) throws E {
final Map, Collection> raw = ACollectionHelper.groupBy(this, f, keyEquality);
AMap result = AHashMap.empty(keyEquality);
for(Map.Entry, Collection> entry: raw.entrySet()) {
result = result.updated(entry.getKey().value, createInternal(entry.getValue()));
}
return result;
}
@Override public AOption find(APredicate pred) throws E {
return ACollectionHelper.find(this, pred);
}
@Override public boolean forAll(APredicate pred) throws E {
return ACollectionHelper.forAll(this, pred);
}
@Override public boolean exists(APredicate pred) throws E {
return ACollectionHelper.exists(this, pred);
}
@Override public AList toList() {
return AList.create(this);
}
@Override public AHashSet toSet() {
return AHashSet.create(this);
}
@Override public AHashSet toSet(AEquality equality) {
return AHashSet.create(equality, this);
}
@Override public String mkString() {
return ACollectionHelper.mkString(this);
}
@Override public String mkString(String separator) {
return ACollectionHelper.mkString(this, separator);
}
@Override public String mkString(String prefix, String separator, String suffix) {
return ACollectionHelper.mkString(this, prefix, separator, suffix);
}
@Override public String toString() {
return mkString("[", ", ", "]");
}
@Override public boolean equals (Object o) {
if (this == o) return true;
if (o == null || getClass() != o.getClass()) return false;
if(size() != ((ACollection)o).size()) return false;
final Iterator _this = iterator();
final Iterator _that = ((ACollection)o).iterator();
while(_this.hasNext()) {
if(! AEquality.EQUALS.equals(_this.next(), _that.next())) {
return false;
}
}
return true;
}
@Override public int hashCode() {
int result = 0;
for(T o: this) {
result = 31*result + (o != null ? equalityForEquals().hashCode(o) : 0);
}
return result;
}
//--------------------- java.util.Collection methods
@Override public boolean contains(final Object o) {
return find(new APredicateNoThrow() {
@Override public boolean apply(T candidate) {
return equalityForEquals().equals(o, candidate);
}
}).isDefined();
}
@SuppressWarnings("NullableProblems")
@Override public Object[] toArray() {
final Object[] result = new Object[size()];
int i = 0;
for(T o: this) {
result[i++] = o;
}
return result;
}
@SuppressWarnings({"unchecked", "NullableProblems"})
@Override public T1[] toArray(T1[] a) {
if(a.length < size()) {
a = (T1[]) Array.newInstance(a.getClass().getComponentType());
}
int i = 0;
for(T o: this) {
a[i++] = (T1) o;
}
if(a.length > size()) {
a[size()] = null;
}
return a;
}
@Override public boolean add(T t) {
throw new UnsupportedOperationException();
}
@Override public boolean remove(Object o) {
throw new UnsupportedOperationException();
}
@SuppressWarnings("NullableProblems")
@Override
public boolean containsAll(Collection c) {
for(Object o: c) {
if(! contains(o)) {
return false;
}
}
return true;
}
@SuppressWarnings("NullableProblems")
@Override
public boolean addAll(Collection c) {
throw new UnsupportedOperationException();
}
@SuppressWarnings("NullableProblems")
@Override
public boolean removeAll(Collection c) {
throw new UnsupportedOperationException();
}
@SuppressWarnings("NullableProblems")
@Override
public boolean retainAll(Collection c) {
throw new UnsupportedOperationException();
}
@Override
public void clear() {
throw new UnsupportedOperationException();
}
}