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Library providing immutable/persistent collection classes for Java. While collections are immutable they provide methods for adding and removing values by creating new modified copies of themselves. Each copy shares almost all of its structure with other copies to minimize memory consumption.
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//
// Burton Computer Corporation
// http://www.burton-computer.com
//
// Copyright (c) 2017, Burton Computer Corporation
// All rights reserved.
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package org.javimmutable.collections.common;

import org.javimmutable.collections.Cursor;
import org.javimmutable.collections.IterableStreamable;
import org.javimmutable.collections.JImmutableMap;
import org.javimmutable.collections.MapEntry;
import org.javimmutable.collections.cursors.TransformCursor;
import org.javimmutable.collections.iterators.TransformStreamable;

import javax.annotation.Nonnull;
import javax.annotation.Nullable;
import javax.annotation.concurrent.Immutable;
import java.util.Map;

@Immutable
public abstract class AbstractJImmutableMap
    implements JImmutableMap
{
    @Nullable
    @Override
    public V get(K key)
    {
        return getValueOr(key, null);
    }

    /**
     * Adds the key/value pair to this map.  Any value already existing for the specified key
     * is replaced with the new value.
     */
    @Override
    @Nonnull
    public JImmutableMap insert(@Nonnull Entry e)
    {
        return assign(e.getKey(), e.getValue());
    }

    @Nonnull
    @Override
    public JImmutableMap getInsertableSelf()
    {
        return this;
    }

    @Nonnull
    @Override
    public JImmutableMap assignAll(@Nonnull JImmutableMap map)
    {
        return assignAllHelper(map);
    }

    @Nonnull
    @Override
    public JImmutableMap assignAll(@Nonnull Map map)
    {
        JImmutableMap answer = this;
        for (Map.Entry e : map.entrySet()) {
            answer = answer.assign(e.getKey(), e.getValue());
        }
        return answer;
    }

    @Override
    public boolean isEmpty()
    {
        return size() == 0;
    }

    @Nonnull
    @Override
    public Cursor keysCursor()
    {
        return TransformCursor.ofKeys(cursor());
    }

    @Nonnull
    @Override
    public Cursor valuesCursor()
    {
        return TransformCursor.ofValues(cursor());
    }

    @Nonnull
    @Override
    public Map getMap()
    {
        return MapAdaptor.of(this);
    }

    @Nonnull
    @Override
    public IterableStreamable keys()
    {
        return TransformStreamable.ofKeys(this);
    }

    @Nonnull
    @Override
    public IterableStreamable values()
    {
        return TransformStreamable.ofValues(this);
    }

    @Override
    public int hashCode()
    {
        return getMap().hashCode();
    }

    @Override
    public boolean equals(Object o)
    {
        if (o == this) {
            return true;
        } else if (o instanceof JImmutableMap) {
            return getMap().equals(((JImmutableMap)o).getMap());
        } else {
            return (o instanceof Map) && getMap().equals(o);
        }
    }

    @Override
    public String toString()
    {
        StringBuilder sb = new StringBuilder();
        sb.append("{");
        for (Cursor> cursor = cursor().start(); cursor.hasValue(); cursor = cursor.next()) {
            if (sb.length() > 1) {
                sb.append(", ");
            }
            MapEntry.addToString(sb, cursor.getValue());
        }
        sb.append("}");
        return sb.toString();
    }

    public int getSpliteratorCharacteristics()
    {
        return StreamConstants.SPLITERATOR_UNORDERED;
    }

    //resolves generics issue in assignAll(JImmutableMap). See Effective Java, Item 28
    @Nonnull
    private  JImmutableMap assignAllHelper(@Nonnull JImmutableMap map)
    {
        JImmutableMap answer = this;
        Cursor> c = map.cursor();
        for (c = c.start(); c.hasValue(); c = c.next()) {
            Entry e = c.getValue();
            answer = answer.assign(e.getKey(), e.getValue());
        }
        return answer;
    }
}