datsun$ cat url4.java
import java.net.*;

public class url4 {

    public static void main(String args[]) {
        try {
            URL u = new URL(new URL(args[0]), args[1]);
            System.out.println("URL: " + u.toString());
        } catch (Exception e) {
            System.out.println(e);
        }
    }
}
datsun$ /usr/local/java/jdk1.2/solaris/bin/java url4 file:/x/y/z a
URL: file:/x/y/a
datsun$ /usr/local/java/jdk1.1.6/solaris/bin/java url4 file:/x/y/z a
URL: file:/x/y/a
datsun$ /usr/local/java/jdk1.2/solaris/bin/java url4 file:/x/y/z ../../a
URL: file:/x/y//a
datsun$ /usr/local/java/jdk1.1.6/solaris/bin/java url4 file:/x/y/z ../../a
URL: file:/a
datsun$ /usr/local/java/jdk1.2/solaris/bin/java url4 file:/x/y/z ../a
URL: file:/x/y/../a
datsun$ /usr/local/java/jdk1.1.6/solaris/bin/java url4 file:/x/y/z ../a
URL: file:/x/a

Note how all the cases involving .. are handled quite differently from 1.1.6.

This is preventing HotJava Views from working on JDK 1.2.