JSONObject.java

package org.json;

import java.io.Closeable;

/*
 Copyright (c) 2002 JSON.org

 Permission is hereby granted, free of charge, to any person obtaining a copy
 of this software and associated documentation files (the "Software"), to deal
 in the Software without restriction, including without limitation the rights
 to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
 copies of the Software, and to permit persons to whom the Software is
 furnished to do so, subject to the following conditions:

 The above copyright notice and this permission notice shall be included in all
 copies or substantial portions of the Software.

 The Software shall be used for Good, not Evil.

 THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
 IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
 FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
 AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
 LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
 OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
 SOFTWARE.
 */

import java.io.IOException;
import java.io.StringWriter;
import java.io.Writer;
import java.lang.annotation.Annotation;
import java.lang.reflect.Field;
import java.lang.reflect.InvocationTargetException;
import java.lang.reflect.Method;
import java.lang.reflect.Modifier;
import java.math.BigDecimal;
import java.math.BigInteger;
import java.util.Collection;
import java.util.Enumeration;
import java.util.HashMap;
import java.util.Iterator;
import java.util.LinkedHashMap;
import java.util.Locale;
import java.util.Map;
import java.util.Map.Entry;
import java.util.ResourceBundle;
import java.util.Set;
import java.util.regex.Pattern;

/**
 * A JSONObject is an unordered collection of name/value pairs. Its external
 * form is a string wrapped in curly braces with colons between the names and
 * values, and commas between the values and names. The internal form is an
 * object having <code>get</code> and <code>opt</code> methods for accessing
 * the values by name, and <code>put</code> methods for adding or replacing
 * values by name. The values can be any of these types: <code>Boolean</code>,
 * <code>JSONArray</code>, <code>JSONObject</code>, <code>Number</code>,
 * <code>String</code>, or the <code>JSONObject.NULL</code> object. A
 * JSONObject constructor can be used to convert an external form JSON text
 * into an internal form whose values can be retrieved with the
 * <code>get</code> and <code>opt</code> methods, or to convert values into a
 * JSON text using the <code>put</code> and <code>toString</code> methods. A
 * <code>get</code> method returns a value if one can be found, and throws an
 * exception if one cannot be found. An <code>opt</code> method returns a
 * default value instead of throwing an exception, and so is useful for
 * obtaining optional values.
 * <p>
 * The generic <code>get()</code> and <code>opt()</code> methods return an
 * object, which you can cast or query for type. There are also typed
 * <code>get</code> and <code>opt</code> methods that do type checking and type
 * coercion for you. The opt methods differ from the get methods in that they
 * do not throw. Instead, they return a specified value, such as null.
 * <p>
 * The <code>put</code> methods add or replace values in an object. For
 * example,
 *
 * <pre>
 * myString = new JSONObject()
 *         .put(&quot;JSON&quot;, &quot;Hello, World!&quot;).toString();
 * </pre>
 *
 * produces the string <code>{"JSON": "Hello, World"}</code>.
 * <p>
 * The texts produced by the <code>toString</code> methods strictly conform to
 * the JSON syntax rules. The constructors are more forgiving in the texts they
 * will accept:
 * <ul>
 * <li>An extra <code>,</code>&nbsp;<small>(comma)</small> may appear just
 * before the closing brace.</li>
 * <li>Strings may be quoted with <code>'</code>&nbsp;<small>(single
 * quote)</small>.</li>
 * <li>Strings do not need to be quoted at all if they do not begin with a
 * quote or single quote, and if they do not contain leading or trailing
 * spaces, and if they do not contain any of these characters:
 * <code>{ } [ ] / \ : , #</code> and if they do not look like numbers and
 * if they are not the reserved words <code>true</code>, <code>false</code>,
 * or <code>null</code>.</li>
 * </ul>
 *
 * @author JSON.org
 * @version 2016-08-15
 */
public class JSONObject {
    /**
     * JSONObject.NULL is equivalent to the value that JavaScript calls null,
     * whilst Java's null is equivalent to the value that JavaScript calls
     * undefined.
     */
    private static final class Null {

        /**
         * There is only intended to be a single instance of the NULL object,
         * so the clone method returns itself.
         *
         * @return NULL.
         */
        @Override
        protected final Object clone() {
            return this;
        }

        /**
         * A Null object is equal to the null value and to itself.
         *
         * @param object
         *            An object to test for nullness.
         * @return true if the object parameter is the JSONObject.NULL object or
         *         null.
         */
        @Override
        public boolean equals(Object object) {
            return object == null || object == this;
        }
        /**
         * A Null object is equal to the null value and to itself.
         *
         * @return always returns 0.
         */
        @Override
        public int hashCode() {
            return 0;
        }

        /**
         * Get the "null" string value.
         *
         * @return The string "null".
         */
        @Override
        public String toString() {
            return "null";
        }
    }
    
    /**
     *  Regular Expression Pattern that matches JSON Numbers. This is primarily used for
     *  output to guarantee that we are always writing valid JSON. 
     */
    static final Pattern NUMBER_PATTERN = Pattern.compile("-?(?:0|[1-9]\\d*)(?:\\.\\d+)?(?:[eE][+-]?\\d+)?");

    /**
     * The map where the JSONObject's properties are kept.
     */
    private final Map<String, Object> map;

    /**
     * It is sometimes more convenient and less ambiguous to have a
     * <code>NULL</code> object than to use Java's <code>null</code> value.
     * <code>JSONObject.NULL.equals(null)</code> returns <code>true</code>.
     * <code>JSONObject.NULL.toString()</code> returns <code>"null"</code>.
     */
    public static final Object NULL = new Null();

    /**
     * Construct an empty JSONObject.
     */
    public JSONObject() {
        // HashMap is used on purpose to ensure that elements are unordered by 
        // the specification.
        // JSON tends to be a portable transfer format to allows the container 
        // implementations to rearrange their items for a faster element 
        // retrieval based on associative access.
        // Therefore, an implementation mustn't rely on the order of the item.
        this.map = new LinkedHashMap<String, Object>();
    }

    /**
     * Construct a JSONObject from a subset of another JSONObject. An array of
     * strings is used to identify the keys that should be copied. Missing keys
     * are ignored.
     *
     * @param jo
     *            A JSONObject.
     * @param names
     *            An array of strings.
     */
    public JSONObject(JSONObject jo, String ... names) {
        this(names.length);
        for (int i = 0; i < names.length; i += 1) {
            try {
                this.putOnce(names[i], jo.opt(names[i]));
            } catch (Exception ignore) {
            }
        }
    }

    /**
     * Construct a JSONObject from a JSONTokener.
     *
     * @param x
     *            A JSONTokener object containing the source string.
     * @throws JSONException
     *             If there is a syntax error in the source string or a
     *             duplicated key.
     */
    public JSONObject(JSONTokener x) throws JSONException {
        this();
        char c;
        String key;

        if (x.nextClean() != '{') {
            throw x.syntaxError("A JSONObject text must begin with '{'");
        }
        for (;;) {
            c = x.nextClean();
            switch (c) {
            case 0:
                throw x.syntaxError("A JSONObject text must end with '}'");
            case '}':
                return;
            default:
                x.back();
                key = x.nextValue().toString();
            }

            // The key is followed by ':'.

            c = x.nextClean();
            if (c != ':') {
                throw x.syntaxError("Expected a ':' after a key");
            }
            
            // Use syntaxError(..) to include error location
            
            if (key != null) {
                // Check if key exists
                if (this.opt(key) != null) {
                    // key already exists
                    throw x.syntaxError("Duplicate key \"" + key + "\"");
                }
                // Only add value if non-null
                Object value = x.nextValue();
                if (value!=null) {
                    this.put(key, value);
                }
            }

            // Pairs are separated by ','.

            switch (x.nextClean()) {
            case ';':
            case ',':
                if (x.nextClean() == '}') {
                    return;
                }
                x.back();
                break;
            case '}':
                return;
            default:
                throw x.syntaxError("Expected a ',' or '}'");
            }
        }
    }

    /**
     * Construct a JSONObject from a Map.
     *
     * @param m
     *            A  object that can be used to initialize the contents of
     *            the JSONObject.
     * @throws JSONException
     *            If a value in the  is non-finite number.
     * @throws NullPointerException
     *            If a key in the  is <code>null</code>
     */
    public JSONObject(Map<?, ?> m) {
        if (m == null) {
            this.map = new LinkedHashMap<String, Object>();
        } else {
            this.map = new LinkedHashMap<String, Object>(m.size());
        	for (final Entry<?, ?> e : m.entrySet()) {
        	    if(e.getKey() == null) {
        	        throw new NullPointerException("Null key.");
        	    }
                final Object value = e.getValue();
                if (value != null) {
                    this.map.put(String.valueOf(e.getKey()), wrap(value));
                }
            }
        }
    }

    /**
     * Construct a JSONObject from an Object using bean getters. It reflects on
     * all of the public methods of the object. For each of the methods with no
     * parameters and a name starting with <code>"get"</code> or
     * <code>"is"</code> followed by an uppercase letter, the method is invoked,
     * and a key and the value returned from the getter method are put into the
     * new JSONObject.
     * <p>
     * The key is formed by removing the <code>"get"</code> or <code>"is"</code>
     * prefix. If the second remaining character is not upper case, then the
     * first character is converted to lower case.
     * <p>
     * Methods that are <code>static</code>, return <code>void</code>,
     * have parameters, or are "bridge" methods, are ignored.
     * <p>
     * For example, if an object has a method named <code>"getName"</code>, and
     * if the result of calling <code>object.getName()</code> is
     * <code>"Larry Fine"</code>, then the JSONObject will contain
     * <code>"name": "Larry Fine"</code>.
     * <p>
     * The {@link JSONPropertyName} annotation can be used on a bean getter to
     * override key name used in the JSONObject. For example, using the object
     * above with the <code>getName</code> method, if we annotated it with:
     * <pre>
     * &#64;JSONPropertyName("FullName")
     * public String getName() { return this.name; }
     * </pre>
     * The resulting JSON object would contain <code>"FullName": "Larry Fine"</code>
     * <p>
     * Similarly, the {@link JSONPropertyName} annotation can be used on non-
     * <code>get</code> and <code>is</code> methods. We can also override key
     * name used in the JSONObject as seen below even though the field would normally
     * be ignored:
     * <pre>
     * &#64;JSONPropertyName("FullName")
     * public String fullName() { return this.name; }
     * </pre>
     * The resulting JSON object would contain <code>"FullName": "Larry Fine"</code>
     * <p>
     * The {@link JSONPropertyIgnore} annotation can be used to force the bean property
     * to not be serialized into JSON. If both {@link JSONPropertyIgnore} and
     * {@link JSONPropertyName} are defined on the same method, a depth comparison is
     * performed and the one closest to the concrete class being serialized is used.
     * If both annotations are at the same level, then the {@link JSONPropertyIgnore}
     * annotation takes precedent and the field is not serialized.
     * For example, the following declaration would prevent the <code>getName</code>
     * method from being serialized:
     * <pre>
     * &#64;JSONPropertyName("FullName")
     * &#64;JSONPropertyIgnore 
     * public String getName() { return this.name; }
     * </pre>
     * <p>
     * 
     * @param bean
     *            An object that has getter methods that should be used to make
     *            a JSONObject.
     */
    public JSONObject(Object bean) {
        this();
        this.populateMap(bean);
    }

    /**
     * Construct a JSONObject from an Object, using reflection to find the
     * public members. The resulting JSONObject's keys will be the strings from
     * the names array, and the values will be the field values associated with
     * those keys in the object. If a key is not found or not visible, then it
     * will not be copied into the new JSONObject.
     *
     * @param object
     *            An object that has fields that should be used to make a
     *            JSONObject.
     * @param names
     *            An array of strings, the names of the fields to be obtained
     *            from the object.
     */
    public JSONObject(Object object, String ... names) {
        this(names.length);
        Class<?> c = object.getClass();
        for (int i = 0; i < names.length; i += 1) {
            String name = names[i];
            try {
                this.putOpt(name, c.getField(name).get(object));
            } catch (Exception ignore) {
            }
        }
    }

    /**
     * Construct a JSONObject from a source JSON text string. This is the most
     * commonly used JSONObject constructor.
     *
     * @param source
     *            A string beginning with <code>{</code>&nbsp;<small>(left
     *            brace)</small> and ending with <code>}</code>
     *            &nbsp;<small>(right brace)</small>.
     * @exception JSONException
     *                If there is a syntax error in the source string or a
     *                duplicated key.
     */
    public JSONObject(String source) throws JSONException {
        this(new JSONTokener(source));
    }

    /**
     * Construct a JSONObject from a ResourceBundle.
     *
     * @param baseName
     *            The ResourceBundle base name.
     * @param locale
     *            The Locale to load the ResourceBundle for.
     * @throws JSONException
     *             If any JSONExceptions are detected.
     */
    public JSONObject(String baseName, Locale locale) throws JSONException {
        this();
        ResourceBundle bundle = ResourceBundle.getBundle(baseName, locale,
                Thread.currentThread().getContextClassLoader());

// Iterate through the keys in the bundle.

        Enumeration<String> keys = bundle.getKeys();
        while (keys.hasMoreElements()) {
            Object key = keys.nextElement();
            if (key != null) {

// Go through the path, ensuring that there is a nested JSONObject for each
// segment except the last. Add the value using the last segment's name into
// the deepest nested JSONObject.

                String[] path = ((String) key).split("\\.");
                int last = path.length - 1;
                JSONObject target = this;
                for (int i = 0; i < last; i += 1) {
                    String segment = path[i];
                    JSONObject nextTarget = target.optJSONObject(segment);
                    if (nextTarget == null) {
                        nextTarget = new JSONObject();
                        target.put(segment, nextTarget);
                    }
                    target = nextTarget;
                }
                target.put(path[last], bundle.getString((String) key));
            }
        }
    }
    
    /**
     * Constructor to specify an initial capacity of the internal map. Useful for library 
     * internal calls where we know, or at least can best guess, how big this JSONObject
     * will be.
     * 
     * @param initialCapacity initial capacity of the internal map.
     */
    protected JSONObject(int initialCapacity){
        this.map = new LinkedHashMap<String, Object>(initialCapacity);
    }

    /**
     * Accumulate values under a key. It is similar to the put method except
     * that if there is already an object stored under the key then a JSONArray
     * is stored under the key to hold all of the accumulated values. If there
     * is already a JSONArray, then the new value is appended to it. In
     * contrast, the put method replaces the previous value.
     *
     * If only one value is accumulated that is not a JSONArray, then the result
     * will be the same as using put. But if multiple values are accumulated,
     * then the result will be like append.
     *
     * @param key
     *            A key string.
     * @param value
     *            An object to be accumulated under the key.
     * @return this.
     * @throws JSONException
     *            If the value is non-finite number.
     * @throws NullPointerException
     *            If the key is <code>null</code>.
     */
    public JSONObject accumulate(String key, Object value) throws JSONException {
        testValidity(value);
        Object object = this.opt(key);
        if (object == null) {
            this.put(key,
                    value instanceof JSONArray ? new JSONArray().put(value)
                            : value);
        } else if (object instanceof JSONArray) {
            ((JSONArray) object).put(value);
        } else {
            this.put(key, new JSONArray().put(object).put(value));
        }
        return this;
    }

    /**
     * Append values to the array under a key. If the key does not exist in the
     * JSONObject, then the key is put in the JSONObject with its value being a
     * JSONArray containing the value parameter. If the key was already
     * associated with a JSONArray, then the value parameter is appended to it.
     *
     * @param key
     *            A key string.
     * @param value
     *            An object to be accumulated under the key.
     * @return this.
     * @throws JSONException
     *            If the value is non-finite number or if the current value associated with
     *             the key is not a JSONArray.
     * @throws NullPointerException
     *            If the key is <code>null</code>.
     */
    public JSONObject append(String key, Object value) throws JSONException {
        testValidity(value);
        Object object = this.opt(key);
        if (object == null) {
            this.put(key, new JSONArray().put(value));
        } else if (object instanceof JSONArray) {
            this.put(key, ((JSONArray) object).put(value));
        } else {
            throw wrongValueFormatException(key, "JSONArray", null, null);
        }
        return this;
    }

    /**
     * Produce a string from a double. The string "null" will be returned if the
     * number is not finite.
     *
     * @param d
     *            A double.
     * @return A String.
     */
    public static String doubleToString(double d) {
        if (Double.isInfinite(d) || Double.isNaN(d)) {
            return "null";
        }

// Shave off trailing zeros and decimal point, if possible.

        String string = Double.toString(d);
        if (string.indexOf('.') > 0 && string.indexOf('e') < 0
                && string.indexOf('E') < 0) {
            while (string.endsWith("0")) {
                string = string.substring(0, string.length() - 1);
            }
            if (string.endsWith(".")) {
                string = string.substring(0, string.length() - 1);
            }
        }
        return string;
    }

    /**
     * Get the value object associated with a key.
     *
     * @param key
     *            A key string.
     * @return The object associated with the key.
     * @throws JSONException
     *             if the key is not found.
     */
    public Object get(String key) throws JSONException {
        if (key == null) {
            throw new JSONException("Null key.");
        }
        Object object = this.opt(key);
        if (object == null) {
            throw new JSONException("JSONObject[" + quote(key) + "] not found.");
        }
        return object;
    }

    /**
     * Get the enum value associated with a key.
     * 
     * @param <E>
     *            Enum Type
     * @param clazz
     *           The type of enum to retrieve.
     * @param key
     *           A key string.
     * @return The enum value associated with the key
     * @throws JSONException
     *             if the key is not found or if the value cannot be converted
     *             to an enum.
     */
    public <E extends Enum<E>> E getEnum(Class<E> clazz, String key) throws JSONException {
        E val = optEnum(clazz, key);
        if(val==null) {
            // JSONException should really take a throwable argument.
            // If it did, I would re-implement this with the Enum.valueOf
            // method and place any thrown exception in the JSONException
            throw wrongValueFormatException(key, "enum of type " + quote(clazz.getSimpleName()), null);
        }
        return val;
    }

    /**
     * Get the boolean value associated with a key.
     *
     * @param key
     *            A key string.
     * @return The truth.
     * @throws JSONException
     *             if the value is not a Boolean or the String "true" or
     *             "false".
     */
    public boolean getBoolean(String key) throws JSONException {
        Object object = this.get(key);
        if (object.equals(Boolean.FALSE)
                || (object instanceof String && ((String) object)
                        .equalsIgnoreCase("false"))) {
            return false;
        } else if (object.equals(Boolean.TRUE)
                || (object instanceof String && ((String) object)
                        .equalsIgnoreCase("true"))) {
            return true;
        }
        throw wrongValueFormatException(key, "Boolean", null);
    }

    /**
     * Get the BigInteger value associated with a key.
     *
     * @param key
     *            A key string.
     * @return The numeric value.
     * @throws JSONException
     *             if the key is not found or if the value cannot 
     *             be converted to BigInteger.
     */
    public BigInteger getBigInteger(String key) throws JSONException {
        Object object = this.get(key);
        BigInteger ret = objectToBigInteger(object, null);
        if (ret != null) {
            return ret;
        }
        throw wrongValueFormatException(key, "BigInteger", object, null);
    }

    /**
     * Get the BigDecimal value associated with a key. If the value is float or
     * double, the the {@link BigDecimal#BigDecimal(double)} constructor will
     * be used. See notes on the constructor for conversion issues that may
     * arise.
     *
     * @param key
     *            A key string.
     * @return The numeric value.
     * @throws JSONException
     *             if the key is not found or if the value
     *             cannot be converted to BigDecimal.
     */
    public BigDecimal getBigDecimal(String key) throws JSONException {
        Object object = this.get(key);
        BigDecimal ret = objectToBigDecimal(object, null);
        if (ret != null) {
            return ret;
        }
        throw wrongValueFormatException(key, "BigDecimal", object, null);
    }

    /**
     * Get the double value associated with a key.
     *
     * @param key
     *            A key string.
     * @return The numeric value.
     * @throws JSONException
     *             if the key is not found or if the value is not a Number
     *             object and cannot be converted to a number.
     */
    public double getDouble(String key) throws JSONException {
        final Object object = this.get(key);
        if(object instanceof Number) {
            return ((Number)object).doubleValue();
        }
        try {
            return Double.parseDouble(object.toString());
        } catch (Exception e) {
            throw wrongValueFormatException(key, "double", e);
        }
    }

    /**
     * Get the float value associated with a key.
     *
     * @param key
     *            A key string.
     * @return The numeric value.
     * @throws JSONException
     *             if the key is not found or if the value is not a Number
     *             object and cannot be converted to a number.
     */
    public float getFloat(String key) throws JSONException {
        final Object object = this.get(key);
        if(object instanceof Number) {
            return ((Number)object).floatValue();
        }
        try {
            return Float.parseFloat(object.toString());
        } catch (Exception e) {
            throw wrongValueFormatException(key, "float", e);
        }
    }

    /**
     * Get the Number value associated with a key.
     *
     * @param key
     *            A key string.
     * @return The numeric value.
     * @throws JSONException
     *             if the key is not found or if the value is not a Number
     *             object and cannot be converted to a number.
     */
    public Number getNumber(String key) throws JSONException {
        Object object = this.get(key);
        try {
            if (object instanceof Number) {
                return (Number)object;
            }
            return stringToNumber(object.toString());
        } catch (Exception e) {
            throw wrongValueFormatException(key, "number", e);
        }
    }

    /**
     * Get the int value associated with a key.
     *
     * @param key
     *            A key string.
     * @return The integer value.
     * @throws JSONException
     *             if the key is not found or if the value cannot be converted
     *             to an integer.
     */
    public int getInt(String key) throws JSONException {
        final Object object = this.get(key);
        if(object instanceof Number) {
            return ((Number)object).intValue();
        }
        try {
            return Integer.parseInt(object.toString());
        } catch (Exception e) {
            throw wrongValueFormatException(key, "int", e);
        }
    }

    /**
     * Get the JSONArray value associated with a key.
     *
     * @param key
     *            A key string.
     * @return A JSONArray which is the value.
     * @throws JSONException
     *             if the key is not found or if the value is not a JSONArray.
     */
    public JSONArray getJSONArray(String key) throws JSONException {
        Object object = this.get(key);
        if (object instanceof JSONArray) {
            return (JSONArray) object;
        }
        throw wrongValueFormatException(key, "JSONArray", null);
    }

    /**
     * Get the JSONObject value associated with a key.
     *
     * @param key
     *            A key string.
     * @return A JSONObject which is the value.
     * @throws JSONException
     *             if the key is not found or if the value is not a JSONObject.
     */
    public JSONObject getJSONObject(String key) throws JSONException {
        Object object = this.get(key);
        if (object instanceof JSONObject) {
            return (JSONObject) object;
        }
        throw wrongValueFormatException(key, "JSONObject", null);
    }

    /**
     * Get the long value associated with a key.
     *
     * @param key
     *            A key string.
     * @return The long value.
     * @throws JSONException
     *             if the key is not found or if the value cannot be converted
     *             to a long.
     */
    public long getLong(String key) throws JSONException {
        final Object object = this.get(key);
        if(object instanceof Number) {
            return ((Number)object).longValue();
        }
        try {
            return Long.parseLong(object.toString());
        } catch (Exception e) {
            throw wrongValueFormatException(key, "long", e);
        }
    }

    /**
     * Get an array of field names from a JSONObject.
     *
     * @param jo
     *            JSON object
     * @return An array of field names, or null if there are no names.
     */
    public static String[] getNames(JSONObject jo) {
        if (jo.isEmpty()) {
            return null;
        }
        return jo.keySet().toArray(new String[jo.length()]);
    }

    /**
     * Get an array of public field names from an Object.
     *
     * @param object
     *            object to read
     * @return An array of field names, or null if there are no names.
     */
    public static String[] getNames(Object object) {
        if (object == null) {
            return null;
        }
        Class<?> klass = object.getClass();
        Field[] fields = klass.getFields();
        int length = fields.length;
        if (length == 0) {
            return null;
        }
        String[] names = new String[length];
        for (int i = 0; i < length; i += 1) {
            names[i] = fields[i].getName();
        }
        return names;
    }

    /**
     * Get the string associated with a key.
     *
     * @param key
     *            A key string.
     * @return A string which is the value.
     * @throws JSONException
     *             if there is no string value for the key.
     */
    public String getString(String key) throws JSONException {
        Object object = this.get(key);
        if (object instanceof String) {
            return (String) object;
        }
        throw wrongValueFormatException(key, "string", null);
    }

    /**
     * Determine if the JSONObject contains a specific key.
     *
     * @param key
     *            A key string.
     * @return true if the key exists in the JSONObject.
     */
    public boolean has(String key) {
        return this.map.containsKey(key);
    }

    /**
     * Increment a property of a JSONObject. If there is no such property,
     * create one with a value of 1 (Integer). If there is such a property, and if it is
     * an Integer, Long, Double, Float, BigInteger, or BigDecimal then add one to it.
     * No overflow bounds checking is performed, so callers should initialize the key
     * prior to this call with an appropriate type that can handle the maximum expected
     * value.
     *
     * @param key
     *            A key string.
     * @return this.
     * @throws JSONException
     *             If there is already a property with this name that is not an
     *             Integer, Long, Double, or Float.
     */
    public JSONObject increment(String key) throws JSONException {
        Object value = this.opt(key);
        if (value == null) {
            this.put(key, 1);
        } else if (value instanceof Integer) {
            this.put(key, ((Integer) value).intValue() + 1);
        } else if (value instanceof Long) {
            this.put(key, ((Long) value).longValue() + 1L);
        } else if (value instanceof BigInteger) {
            this.put(key, ((BigInteger)value).add(BigInteger.ONE));
        } else if (value instanceof Float) {
            this.put(key, ((Float) value).floatValue() + 1.0f);
        } else if (value instanceof Double) {
            this.put(key, ((Double) value).doubleValue() + 1.0d);
        } else if (value instanceof BigDecimal) {
            this.put(key, ((BigDecimal)value).add(BigDecimal.ONE));
        } else {
            throw new JSONException("Unable to increment [" + quote(key) + "].");
        }
        return this;
    }

    /**
     * Determine if the value associated with the key is <code>null</code> or if there is no
     * value.
     *
     * @param key
     *            A key string.
     * @return true if there is no value associated with the key or if the value
     *        is the JSONObject.NULL object.
     */
    public boolean isNull(String key) {
        return JSONObject.NULL.equals(this.opt(key));
    }

    /**
     * Get an enumeration of the keys of the JSONObject. Modifying this key Set will also
     * modify the JSONObject. Use with caution.
     *
     * @see Set#iterator()
     * 
     * @return An iterator of the keys.
     */
    public Iterator<String> keys() {
        return this.keySet().iterator();
    }

    /**
     * Get a set of keys of the JSONObject. Modifying this key Set will also modify the
     * JSONObject. Use with caution.
     *
     * @see Map#keySet()
     *
     * @return A keySet.
     */
    public Set<String> keySet() {
        return this.map.keySet();
    }

    /**
     * Get a set of entries of the JSONObject. These are raw values and may not
     * match what is returned by the JSONObject get* and opt* functions. Modifying 
     * the returned EntrySet or the Entry objects contained therein will modify the
     * backing JSONObject. This does not return a clone or a read-only view.
     * 
     * Use with caution.
     *
     * @see Map#entrySet()
     *
     * @return An Entry Set
     */
    protected Set<Entry<String, Object>> entrySet() {
        return this.map.entrySet();
    }

    /**
     * Get the number of keys stored in the JSONObject.
     *
     * @return The number of keys in the JSONObject.
     */
    public int length() {
        return this.map.size();
    }

    /**
     * Check if JSONObject is empty.
     *
     * @return true if JSONObject is empty, otherwise false.
     */
    public boolean isEmpty() {
        return this.map.isEmpty();
    }

    /**
     * Produce a JSONArray containing the names of the elements of this
     * JSONObject.
     *
     * @return A JSONArray containing the key strings, or null if the JSONObject
     *        is empty.
     */
    public JSONArray names() {
    	if(this.map.isEmpty()) {
    		return null;
    	}
        return new JSONArray(this.map.keySet());
    }

    /**