java/w8/Box.java

public class Box<T> {
    private T content;
    
    public Box() {}
    
    public Box(T content) {
        this.content = content;
    }
    
    public T getContent() {
        return content;
    }
    
    public void setContent(T content) {
        this.content = content;
    }
    
    public boolean isEmpty() {
        return content == null;
    }
    
    @Override
    public String toString() {
        return "Box{" + "content=" + content + '}';
    }
}