All operations in ND4J and SameDiff are available in "Operation Namespaces". Each namespace is available on the Nd4j and SameDiff classes with its lowercase name.
For example, if you want to use the absoluteDifference operation it would look like this
// ND4J mode
INDArray output = Nd4j.loss.absoluteDifference(labels, predictions, null);
// SameDiff mode
SDVariable output = SameDiff.loss.absoluteDifference(labels, predictions, null);