Microsoft had hoped for a quick ruling that it did not breach Sun's restrictions on Java in its dispute with the firm over Microsoft's use of Java.
The news brings the possibility of a courtroom battle over the use of the cross-platform technology. The judge also dismissed a motion from Sun seeking a ruling that Microsoft is in violation of its licensing agreement.
Sun had filed a lawsuit against Microsoft claiming that it had breached the licensing contract for Java and had made changes to Java in order to tailor it more closely for its Windows platform. Sun says that this makes Microsoft's Java incompatible with other Java software.
A courtroom battle could be long and uncertain because of the complexity of the case.