Erro de método

toda vez que eu que salvo o a Tela inicial apresenta esse erro :

TelaInicial.java:5: error: TelaInicial is not abstract and does not override abstract method actionPerformed (ActionEvent)

public class TelaInicial extends JFrame implements ActionListener

^

e quando eu tento executar a main apresenta esse erro :

Exception in thread “main” java.lang.NoClassDefFoundError: TelaInicial

at Principal.main(Principal.java:3)

Caused by: java.lang.ClassNotFoundException: TelaInicial

at java.base/jdk.internal.loader.BuiltinClassLoader.loadClass(BuiltinClassLoader.java:583)

at java.base/jdk.internal.loader.ClassLoaders$AppClassLoader.loadClass(ClassLoaders.java:178)

at java.base/java.lang.ClassLoader.loadClass(ClassLoader.java:521)

… 1 more

codigo main:

public class Principal{

public static void main (String[] args){

TelaInicial tela = new TelaInicial();

}

}