typediterator.java

thinking in patterns

//: com:bruceeckel:util:TypedIterator.java
package com.bruceeckel.util;
import java.util.*;

public class TypedIterator implements Iterator {
  private Iterator imp;
  private Class type;
  public TypedIterator(Iterator it, Class type) {
    imp = it;
    this.type = type;
  }
  public boolean hasNext() { 
    return imp.hasNext(); 
  }
  public void remove() { imp.remove(); }
  public Object next() {
    Object obj = imp.next();
    if(!type.isInstance(obj))
      throw new ClassCastException(
        "TypedIterator for type " + type +
        " encountered type: " + obj.getClass());
    return obj;
  }
} ///:~