List getter/setter

neutral.java

private final List<Bla> blas = new ArrayList<Bla>();

// foo.setBlas(foo.getBlas()) is neutral, but every getter invocation creates a new List
public List<Bla> getBlas() { return Collections.unmodifiableList(new ArrayList<Bla>(blas)); }

public void setBlas(List<Bla> blas) {
   if (blas != null) {
       this.blas.clear();
       this.blas.addAll(blas);
   }
}

notNeutral.java

private final List<Bla> blas = new ArrayList<Bla>();

// foo.setBlas(foo.getBlas()) is not neutral. it clears the list!
public List<Bla> getBlas() { return Collections.unmodifiableList(blas); }

public void setBlas(List<Bla> blas) {
   if (blas != null) {
       this.blas.clear();
       this.blas.addAll(blas);
   }
}