Something

public abstract class Uttryck
{
public abstract int evaluera();
}
public class Heltal extends Uttryck
{
private int värde;
public Heltal(int värde)
{
this.värde = värde;
}
public int evaluera()
{
return värde;
}
}
public class Addition extends Uttryck
{
private Uttryck uttr1;
private Uttryck uttr2;
public Addition(Uttryck uttr1, Uttryck uttr2)
{
this.uttr1 = uttr1;
this.uttr2 = uttr2;
}
public int evaluera()
{
return uttr1.evaluera() + uttr2.evaluera();
}
}