FilterIteratorImpl

gistfile1.java

/* only output for valid = true */
interface FilterIterator {
  public boolean hasNext();
  public Object next();
}

interface Filter {
  boolean valid(Object o);
}

/* 2 params for constructor, source Iterator, and filter object */
public FilterIteratorImpl implements FilterIterator{

    Iterator i;
    Filter f;
    Object _nextObj = null;
    boolean open = false;
    
    public FilterIteratorImpl(Iterator source,Filter f){
        this.f = f; 
        this.i = source;
        
        //get the root at the first time
        open = true;
        _nextObj = this.next()
        open = false;
        
    }
    
    public boolean hasNext(){
        return null!=_nextObj;
    }
    
    public Object next(){
        // return the root if it is the first time
        if(!open){
            return _nextObj;
            open = true;
        }
        
        //reset the next obj, so we make sure that if we dont have a next one, will be null
        _nextObj = null;
        // keep getting, till we get a valid one
        while(i.hasNext()){
            _nextObj = i.next();
            if(f.valid(_nextObj)) break;
            else _nextObj = null;
        }
        
        return _nextObj;
    }
}