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# JavaObject

The type of a wrapped Java object accessed from within JavaScript code.

Core object |
Implemented in | JavaScript 1.1, NES 2.0

#### Created by

Any Java method which returns an object type. In addition, you can explicitly construct a `JavaObject` using the object's Java constructor with the `Packages` keyword:

    new Packages.JavaClass(parameterList)

where JavaClass is the fully-specified name of the object's Java class.

#### Parameters

    parameterList

An optional list of parameters, specified by the constructor in the Java class.

#### Description

The `JavaObject` object is an instance of a Java class that is created in or passed to JavaScript. `JavaObject` is a wrapper for the instance; all references to the class instance are made through the `JavaObject`. Any Java data brought into JavaScript is converted to JavaScript data types. When the `JavaObject` is passed back to Java, it is unwrapped and can be used by Java code. See the Client-Side JavaScript Guide for more information about data type conversions.

#### Property Summary

Inherits public data members from the Java class of which it is an instance as properties. It also inherits public data members from any superclass as properties.

#### Method Summary

Inherits public methods from the Java class of which it is an instance. The `JavaObject` also inherits methods from `java.lang.Object` and any other superclass.

#### Examples

Example 1. Instantiating a Java object in JavaScript. The following code creates the `JavaObject` `theString`, which is an instance of the class `java.lang.String`:

    var theString = new Packages.java.lang.String("Hello, world")

Because the `String` class is in the `java` package, you can also use the `java` synonym and omit the `Packages` keyword when you instantiate the class:

    var theString = new java.lang.String("Hello, world")

Example 2. Accessing methods of a Java object. Because the `JavaObject` `theString` is an instance of `java.lang.String`, it inherits all the public methods of `java.lang.String`. The following example uses the `startsWith` method to check whether `theString` begins with "Hello".

    var theString = new java.lang.String("Hello, world")
    theString.startsWith("Hello") // returns true

Example 3. Accessing inherited methods. Because `getClass` is a method of `Object`, and `java.lang.String` extends `Object`, the `String` class inherits the `getClass` method. Consequently, `getClass` is also a method of the `JavaObject` which instantiates `String` in JavaScript.

    var theString = new java.lang.String("Hello, world")
    theString.getClass() // returns java.lang.String

#### See also

`JavaArray`, `JavaClass`, `JavaPackage`, `Packages`

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Last Updated: 05/28/99 11:59:41

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