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Simple data-binding that builds directly on jackson-core (streaming), has no other dependencies, and provides additional builder-style content generator

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package com.fasterxml.jackson.jr.ob.impl;

import java.util.*;

/**
 * A specialized {@link java.util.Map} implementation that will collect
 * entries during building, but only materialize full lookup structure
 * when needed; that is, actual building of hash lookup is deferred.
 *
 * Inspired by lazily initialized Map used by Boon library.
 */
public class DeferredMap extends AbstractMap
{
    private Map _map;
    private Object[] _entries;
    private int _end;
    private final boolean _ordered;

    public DeferredMap(boolean ordered) {
        this(ordered, 4);
    }

    public DeferredMap(boolean ordered, int initialSize) {
        _ordered = ordered;
    }

    @Override
    public Object put(Object key, Object value)
    {
        if (_map == null) {
            if (_entries == null) {
                _entries = new Object[8];
            } else if (_end == _entries.length) {
                final int newSize = _newSize(_end);
                _entries = Arrays.copyOf(_entries, newSize);
            }
            _entries[_end] = key;
            _entries[++_end] = value;
            ++_end;
            // here's assuming no dups are added
            return null;
        }
        return _map.put(key, value);
    }
    
    @Override
    public Set> entrySet() {
        buildIfNeeded();
        return _map.entrySet();
    }

    @Override
    public int size() {
        // assuming no dups; otherwise could overestimate
        return (_map == null) ? (_end >> 1) : _map.size();
    }

    @Override
    public boolean isEmpty() {
        return (_map == null) ? (_end == 0) : _map.isEmpty();
    }

    @Override
    public boolean containsValue(Object value) {
        buildIfNeeded();
        return _map.containsValue(value);
    }

    @Override
    public boolean containsKey(Object key) {
        buildIfNeeded();
        return _map.containsKey(key);
    }

    @Override
    public Object get(Object key) {
        buildIfNeeded();
        return _map.get( key );
    }

    @Override
    public Object remove(Object key) {
        buildIfNeeded();
        return _map.remove( key );
    }

    @Override
    public void clear() {
        if (_map != null ) {
            _map.clear();
        } else {
            _end = 0;
        }
    }

    @Override
    public Set