jsonarray.java

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package org.json;

import java.text.ParseException;
import java.util.ArrayList;
import java.util.Collection;
import java.util.NoSuchElementException;

/**
 * A JSONArray is an ordered sequence of values. Its external form is a string
 * wrapped in square brackets with commas between the values. The internal form
 * is an object having get() and opt() methods for accessing the values by
 * index, and put() methods for adding or replacing values. The values can be
 * any of these types: Boolean, JSONArray, JSONObject, Number, String, or the
 * JSONObject.NULL object.
 * <p>
 * The constructor can convert a JSON external form string into an
 * internal form Java object. The toString() method creates an external
 * form string.
 * <p>
 * A get() method returns a value if one can be found, and throws an exception
 * if one cannot be found. An opt() method returns a default value instead of
 * throwing an exception, and so is useful for obtaining optional values.
 * <p>
 * The generic get() and opt() methods return an object which you can cast or
 * query for type. There are also typed get() and opt() methods that do typing
 * checking and type coersion for you.
 * <p>
 * The texts produced by the toString() methods are very strict.
 * 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 bracket.</li>
 * <li>The value null will be inserted when there is <code>,</code>&nbsp;<small>(comma)</small> elision.</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 contain leading
 *     or trailing spaces, and if they do not contain any of these characters:
 *     <code>{ } [ ] / \ : , ' "</code></li>
 * <li>Numbers may have the 0- (octal) or 0x- (hex) prefix.</li>
 * </ul>
 * <p>
 * Public Domain 2002 JSON.org
 * @author JSON.org
 * @version 0.1
 */
public class JSONArray {


    /**
     * The getArrayList where the JSONArray's properties are kept.
     */
    private ArrayList myArrayList;


    /**
     * Construct an empty JSONArray.
     */
    public JSONArray() {
        myArrayList = new ArrayList();
    }


    /**
     * Construct a JSONArray from a JSONTokener.
     * @param x A JSONTokener
     * @exception ParseException A JSONArray must start with '['
     * @exception ParseException Expected a ',' or ']'
     */
    public JSONArray(JSONTokener x) throws ParseException {
        this();
        if (x.nextClean() != '[') {
            throw x.syntaxError("A JSONArray must start with '['");
        }
        if (x.nextClean() == ']') {
            return;
        }
        x.back();
        while (true) {
            if (x.nextClean() == ',') {
                x.back();
                myArrayList.add(null);
            } else {
                x.back();
                myArrayList.add(x.nextValue());
            }
            switch (x.nextClean()) {
            case ',':
                if (x.nextClean() == ']') {
                    return;
                }
                x.back();
                break;
            case ']':
                return;
            default:
                throw x.syntaxError("Expected a ',' or ']'");
            }
        }
    }


    /**
     * Construct a JSONArray from a source string.
     * @param string     A string that begins with 
     * <code>[</code>&nbsp;<small>(left bracket)</small>
     *  and ends with <code>]</code>&nbsp;<small>(right bracket)</small>.
     * @exception ParseException The string must conform to JSON syntax.
     */
    public JSONArray(String string) throws ParseException {
        this(new JSONTokener(string));
    }


    /**
     * Construct a JSONArray from a Collection.
     * @param collection     A Collection.
     */
    public JSONArray(Collection collection) {
        myArrayList = new ArrayList(collection);
    }


    /**
     * Get the object value associated with an index.
     * @param index 
     *  The index must be between 0 and length() - 1.
     * @return An object value.
     * @exception NoSuchElementException
     */
    public Object get(int index) throws NoSuchElementException {
        Object o = opt(index);
        if (o == null) {
            throw new NoSuchElementException("JSONArray[" + index +
                "] not found.");
        }
        return o;
    }


    /**
     * Get the ArrayList which is holding the elements of the JSONArray.
     * @return      The ArrayList.
     */
    ArrayList getArrayList() {
        return myArrayList;
    }


    /**
     * Get the boolean value associated with an index.
     * The string values "true" and "false" are converted to boolean.
     * @param index The index must be between 0 and length() - 1.
     * @return      The truth.
     * @exception NoSuchElementException if the index is not found
     * @exception ClassCastException
     */
    public boolean getBoolean(int index)
            throws ClassCastException, NoSuchElementException {
        Object o = get(index);
        if (o == Boolean.FALSE || o.equals("false")) {
            return false;
        } else if (o == Boolean.TRUE || o.equals("true")) {
            return true;
        }
        throw new ClassCastException("JSONArray[" + index +
            "] not a Boolean.");
    }


    /**
     * Get the double value associated with an index.     
     * @param index The index must be between 0 and length() - 1.
     * @return      The value.
     * @exception NoSuchElementException if the key is not found
     * @exception NumberFormatException
     *  if the value cannot be converted to a number.
     *
     */
    public double getDouble(int index)
            throws NoSuchElementException, NumberFormatException {
        Object o = get(index);
        if (o instanceof Number) {
            return ((Number) o).doubleValue();
        }
        if (o instanceof String) {
            return new Double((String)o).doubleValue();
        }
        throw new NumberFormatException("JSONObject[" +
            index + "] is not a number.");
    }


    /**
     * Get the int value associated with an index.
     * 
     * @param index The index must be between 0 and length() - 1.
     * @return      The value.
     * @exception NoSuchElementException if the key is not found
     * @exception NumberFormatException
     *  if the value cannot be converted to a number.
     *
     */
    public int getInt(int index)
            throws NoSuchElementException, NumberFormatException {
        Object o = get(index);
        if (o instanceof Number) {
            return ((Number)o).intValue();
        }
        return (int)getDouble(index);
    }


    /**
     * Get the JSONArray associated with an index.
     * @param index The index must be between 0 and length() - 1.
     * @return      A JSONArray value.
     * @exception NoSuchElementException if the index is not found or if the
     * value is not a JSONArray
     */
    public JSONArray getJSONArray(int index) throws NoSuchElementException {
        Object o = get(index);
        if (o instanceof JSONArray) {
            return (JSONArray)o;
        }
        throw new NoSuchElementException("JSONArray[" + index +
                "] is not a JSONArray.");
    }


    /**
     * Get the JSONObject associated with an index.
     * @param index subscript
     * @return      A JSONObject value.
     * @exception NoSuchElementException if the index is not found or if the
     * value is not a JSONObject
     */
    public JSONObject getJSONObject(int index) throws NoSuchElementException {
        Object o = get(index);
        if (o instanceof JSONObject) {
            return (JSONObject)o;
        }
        throw new NoSuchElementException("JSONArray[" + index +
            "] is not a JSONObject.");
    }


    /**
     * Get the string associated with an index.
     * @param index The index must be between 0 and length() - 1.
     * @return      A string value.
     * @exception NoSuchElementException
     */
    public String getString(int index) throws NoSuchElementException {
        return get(index).toString();
    }


    /**
     * Determine if the value is null.
     * @param index The index must be between 0 and length() - 1.
     * @return true if the value at the index is null, or if there is no value.
     */
    public boolean isNull(int index) {
        Object o = opt(index);
        return o == null || o.equals(null);
    }


    /**
     * Make a string from the contents of this JSONArray. The separator string
     * is inserted between each element.
     * Warning: This method assumes that the data structure is acyclical.
     * @param separator A string that will be inserted between the elements.
     * @return a string.
     */
    public String join(String separator) {
        int i;
        Object o;
        StringBuffer sb = new StringBuffer();
        for (i = 0; i < myArrayList.size(); i += 1) {
            if (i > 0) {
                sb.append(separator);
            }
            o = myArrayList.get(i);
            if (o == null) {
                sb.append("null");
            } else if (o instanceof String) {
                sb.append(JSONObject.quote((String)o));
            } else if (o instanceof Number) {
                sb.append(JSONObject.numberToString((Number)o));
            } else {
                sb.append(o.toString());
            }
        }
        return sb.toString();
    }


    /**
     * Get the length of the JSONArray.
     *
     * @return The length (or size).
     */
    public int length() {
        return myArrayList.size();
    }


    /**
     * Get the optional object value associated with an index.
     * @param index The index must be between 0 and length() - 1.
     * @return      An object value, or null if there is no
     *              object at that index.
     */
    public Object opt(int index) {
        if (index < 0 || index >= length()) {
            return null;
        } else {
            return myArrayList.get(index);
        }
    }


    /**
     * Get the optional boolean value associated with an index.
     * It returns false if there is no value at that index,
     * or if the value is not Boolean.TRUE or the String "true".
     *
     * @param index The index must be between 0 and length() - 1.
     * @return      The truth.
     */
    public boolean optBoolean(int index)  {
        return optBoolean(index, false);
    }


    /**
     * Get the optional boolean value associated with an index.
     * It returns the defaultValue if there is no value at that index or if it is not
     * a Boolean or the String "true" or "false".
     *
     * @param index The index must be between 0 and length() - 1.
     * @param defaultValue     A boolean default.
     * @return      The truth.
     */
    public boolean optBoolean(int index, boolean defaultValue)  {
        Object o = opt(index);
        if (o != null) {
            if (o == Boolean.FALSE || o.equals("false")) {
                return false;
            } else if (o == Boolean.TRUE || o.equals("true")) {
                return true;
            }
        }
        return defaultValue;
    }