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Java Cookbook
book

Java Cookbook

by Ian F. Darwin
June 2001
Intermediate to advanced content levelIntermediate to advanced
888 pages
21h 1m
English
O'Reilly Media, Inc.
Content preview from Java Cookbook

Converting a Filename to a URL

Problem

You require a URL, but you have a local file.

Solution

Use getResource( ) or File.toURL( ) .

Discussion

There are many operations that require a URL, but for which it would be convenient to refer to a file on the local filesystem or disk. For these, the convenience method getResource( ) in the class java.lang.Class can be used. This takes a filename and returns a URL for it:

public class GetResource { 
    public static void main(String[] argv) { 
        Class c = GetResource.class; 
        java.net.URL u = c.getResource("GetResource.java"); 
        System.out.println(u); 
    } 
}

When I ran this code on Java 2 on my MS-Windows system, it printed:

file:/C:/javasrc/netweb/GetResource.java

Java 2 also introduced a toURL( ) method into the File class (Section 10.2). Unlike getResource( ), this method can throw a MalformedURLException. This makes sense, since a File class can be constructed with arbitrary nonsense in the filename. So the previous code can be rewritten as:

public class FileToURL
{
    public static void main(String[] argv) throws MalformedURLException {
        java.net.URL u = new File("GetResource.java").toURL(  );
        System.out.println(u);
    }
}

Both programs print the same result:

> java FileToURL
file:/usr/home/ian/javasrc/netweb/GetResource.java
> java GetResource
file:/usr/home/ian/javasrc/netweb/GetResource.java
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Publisher Resources

ISBN: 0596001703Supplemental ContentCatalog PageErrata