Abstract variables in Java?

Define a constructor in the abstract class which sets the field so that the concrete implementations are per the specification required to call/override the constructor.

E.g.

public abstract class AbstractTable {
    protected String name;
    
    public AbstractTable(String name) {
        this.name = name;
    }
}

When you extend AbstractTable, the class won’t compile until you add a constructor which calls super("somename").

public class ConcreteTable extends AbstractTable {
    private static final String NAME = "concreteTable";

    public ConcreteTable() {
        super(NAME);
    }
}

This way the implementors are required to set name. This way you can also do (null)checks in the constructor of the abstract class to make it more robust. E.g:

public AbstractTable(String name) {
    Objects.requireNonNull(name, "Name may not be null");
    this.name = name;
}