I can not override methods from Externalizable due to strange weaker access modifier error in java

Question

In documentation says that readExternal() and writeExternal() have default access modifier and I also implement it with default access modifier, but somehow I have 2 error which says that I assign weaker access modifier? So why is that? (I know that using default modifier I can not serializa/deserialize objects from other package)

Error1:

Error:(19, 10) java: readExternal(java.io.ObjectInput) in A cannot implement readExternal(java.io.ObjectInput) in java.io.Externalizable attempting to assign weaker access privileges; was public

Error2:

Error:(16, 10) java: writeExternal(java.io.ObjectOutput) in A cannot implement writeExternal(java.io.ObjectOutput) in java.io.Externalizable attempting to assign weaker access privileges; was public

class A implements Externalizable
{
    public A() {}
    
    @Override
    void writeExternal(ObjectOutput out) throws IOException {}
    
    @Override
    void readExternal(ObjectInput in) throws IOException, ClassNotFoundException {}
}