JavaArray

Summary

Core Object

A wrapped Java array accessed from within JavaScript code is a member of the type JavaArray.

Created by

Any Java method which returns an array. In addition, you can create a JavaArray with an arbitrary data type using the newInstance method of the Array class:

public static Object newInstance(Class componentType,
   int length)
   throws NegativeArraySizeException

Description

The JavaArray object is an instance of a Java array that is created in or passed to JavaScript. JavaArray is a wrapper for the instance; all references to the array instance are made through the JavaArray.

In JavaScript 1.4 and later, the componentType parameter is either a JavaClass object representing the type of the array or class object, such as one returned by java.lang.Class.forName. In JavaScript 1.3 and earlier, componentType must be a class object.

Use zero-based indexes to access the elements in a JavaArray object, just as you do to access elements in an array in Java. For example:

var javaString = new java.lang.String("Hello world!");
var byteArray = javaString.getBytes();
byteArray[0] // returns 72
byteArray[1] // returns 101

Any Java data brought into JavaScript is converted to JavaScript data types. When the JavaArray is passed back to Java, the array is unwrapped and can be used by Java code. See the Core JavaScript 1.5 Guide for more information about data type conversions.

In JavaScript 1.4 and later, the methods of java.lang.Object are inherited by JavaArray.

Backward compatibility

JavaScript 1.3 and earlier

The methods of java.lang.Object are not inherited by JavaArray. In addition, the toString method is inherited from the Object object and returns the following value:

[object JavaArray]

You must specify a class object, such as one returned by java.lang.Object.forName, for the componentType parameter of newInstance when you use this method to create an array. You cannot use a JavaClass object for the componentType parameter.

Properties

length: The number of elements in the Java array represented by JavaArray.

Methods

toString: In JavaScript 1.4, this method is overridden by the inherited method java.lang.Object.toString. in JavaScript 1.3 and earlier, this method returns a string identifying the object as a JavaArray.

In JavaScript 1.4 and later, JavaArray also inherits methods from the Java array superclass, java.lang.Object.

Examples

Example: Instantiating a JavaArray in JavaScript

In this example, the JavaArray byteArray is created by the java.lang.String.getBytes method, which returns an array.

var javaString = new java.lang.String("Hello world!");
var byteArray = javaString.getBytes(); 

Example: Instantiating a JavaArray in JavaScript with the newInstance method

In JavaScript 1.4, you can use a JavaClass object as the argument for the newInstance method which creates the array, as shown in the following code:

var dogs = java.lang.reflect.Array.newInstance(java.lang.String, 5);

In JavaScript 1.1, use a class object returned by java.lang.Class.forName as the argument for the newInstance method, as shown in the following code:

var dataType = java.lang.Class.forName("java.lang.String");
var dogs = java.lang.reflect.Array.newInstance(dataType, 5);