Availability

Netscape 3 LiveConnect

Synopsis

javaarray.length // The length of the array 
javaarray[index] // Read or write an array element

Properties

length

A read-only integer that specifies the number of elements in the Java array represented by the JavaArray object.

Description

The JavaArray object is a JavaScript representation of a Java array that allows JavaScript code to read and write the elements of the array using familiar JavaScript array syntax. In addition, the JavaArray object has a length field that specifies the number of elements in the Java array.

When reading and writing values from array elements, data conversion between JavaScript and Java representations is automatically handled by the system. See Chapter 22 for full details.

Usage

Note that Java arrays differ from JavaScript arrays in a couple of important aspects. First, Java arrays have a fixed length that is specified when they are created. For this reason, the JavaArray length field is read-only. The second difference is that Java arrays are typed (i.e., their elements must all be of the same type of data). Attempting to set an array element to a value of the wrong type results in a JavaScript error or exception.

Example

java.awt.Polygon is a JavaClass object. We can create a JavaObject representing an instance of the class like this:

p = new java.awt.Polygon(  ); 

The object p has properties xpoints and ypoints, which are JavaArray objects representing Java arrays of integers. We can initialize the contents of these arrays with JavaScript code like the following:

for(int i = 0; i < p.xpoints.length; i++)
    p.xpoints[i] = Math.round(Math.random(  )*100);
for(int i = 0; i < p.ypoints.length; i++)
    p.ypoints[i] = Math.round(Math.random(  )*100); 

See Also

getClass( ), JavaClass, JavaObject, JavaPackage, the java property of the Window object; Chapter 22