core/src/main/java/com/orientechnologies/orient/core/metadata/schema/OClassImpl.java
public boolean isSubClassOf(final String iClassName) {
    acquireSchemaReadLock();
    try {
      if (iClassName == null)
        return false;

      if (iClassName.equalsIgnoreCase(getName()) || iClassName.equalsIgnoreCase(getShortName()))
        return true;
      for (OClassImpl superClass : superClasses) {
        if (superClass.isSubClassOf(iClassName))
          return true;
      }
      return false;
    } finally {
      releaseSchemaReadLock();
    }
  }
public boolean isSubClassOf(final String iClassName) {
    acquireSchemaReadLock();
    try {
      if (iClassName == null)
        return false;

      if (iClassName.equalsIgnoreCase(getName()) || iClassName.equalsIgnoreCase(getShortName()))
        return true;
      for (OClassImpl superClass : superClasses) {
        if (superClass.isSubClassOf(iClassName))
          return true;
      }
      return false;
    } finally {
      releaseSchemaReadLock();
    }
  }
Check if the current instance extends specified schema class.

@param iClassName of class that should be checked

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

@see #isSuperClassOf(OClass)