guava/src/com/google/common/reflect/ClassPath.java
public ImmutableSet<ClassInfo> getTopLevelClasses(String packageName) {
    checkNotNull(packageName);
    ImmutableSet.Builder<ClassInfo> builder = ImmutableSet.builder();
    for (ClassInfo classInfo : getTopLevelClasses()) {
      if (classInfo.getPackageName().equals(packageName)) {
        builder.add(classInfo);
      }
    }
    return builder.build();
  }
public ImmutableSet<ClassInfo> getTopLevelClasses(String packageName) {
    checkNotNull(packageName);
    ImmutableSet.Builder<ClassInfo> builder = ImmutableSet.builder();
    for (ClassInfo classInfo : getTopLevelClasses()) {
      if (classInfo.getPackageName().equals(packageName)) {
        builder.add(classInfo);
      }
    }
    return builder.build();
  }
Returns all top level classes whose package name is {@code packageName}.