cdm/src/main/java/ucar/nc2/Group.java
public Group setImmutable() {
    super.setImmutable();
    variables = Collections.unmodifiableList(variables);
    dimensions = Collections.unmodifiableList(dimensions);
    groups = Collections.unmodifiableList(groups);
    attributes.setImmutable();
    return this;
  }
public Group setImmutable() {
    super.setImmutable();
    variables = Collections.unmodifiableList(variables);
    dimensions = Collections.unmodifiableList(dimensions);
    groups = Collections.unmodifiableList(groups);
    attributes.setImmutable();
    return this;
  }
public Group setImmutable ( ) { super . setImmutable ( ) ; variables = Collections . unmodifiableList ( variables ) ; dimensions = Collections . unmodifiableList ( dimensions ) ; groups = Collections . unmodifiableList ( groups ) ; attributes . setImmutable ( ) ; return this ; }
Make this immutable.

@return this
Make this immutable .