I found the answer by myself.
Java Development Kit (JDK) Location
SQL Developer stores the location of the Java Development Kit (JDK) that it is using in a configuration file named product.conf, which is located under the user directory (operating system-specific, as explained in Location of User-Related Information). For example, on a Windows system it might be in a location with the following format:
If you have made an error in your JDK specification or configuration, you can try editing the SetJavaHome line in product.conf.