core/src/main/java/com/orientechnologies/orient/core/metadata/schema/OClassImpl.java
public boolean isSubClassOf(final OClass clazz) {
    acquireSchemaReadLock();
    try {
      if (clazz == null)
        return false;
      if (equals(clazz))
        return true;
      for (OClassImpl superClass : superClasses) {
        if (superClass.isSubClassOf(clazz))
          return true;
      }
      return false;
    } finally {
      releaseSchemaReadLock();
    }
  }
public boolean isSubClassOf(final OClass clazz) {
    acquireSchemaReadLock();
    try {
      if (clazz == null)
        return false;
      if (equals(clazz))
        return true;
      for (OClassImpl superClass : superClasses) {
        if (superClass.isSubClassOf(clazz))
          return true;
      }
      return false;
    } finally {
      releaseSchemaReadLock();
    }
  }
Check if the current instance extends specified schema class.

@param clazz to check

@return true if the current instance extends the passed schema class (iClass)

@see #isSuperClassOf(OClass)