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Copy pathPositiveIntegerIterator.java
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88 lines (75 loc) · 1.97 KB
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import java.util.*;
/*
* Goal: Given an Iterator of type Integer, provide an Iterator<Integer> implementation
* that only provides non-negative values. Only implement next() and hasNext()
*
* Input: Iterator of type Integer
* Output: next() should only ever return positive integers, hasNext() should only return
* true if there is a positive integer ahead in the underlying Iterator
*
* Notes:
* remove() does not need to be implemented
* testIter() is a test case that should pass
*/
public class PositiveIntegerIterator implements Iterator<Integer> {
Iterator<Integer> iterator;
Integer next;
public PositiveIntegerIterator(Iterator<Integer> i) {
//todo
iterator = i;
while (iterator.hasNext()) {
Integer next = iterator.next();
if (next != null && next > 0) {
this.next = next;
break;
}
}
}
@Override
public boolean hasNext() {
//todo
return next != null && next > 0;
}
@Override
public Integer next() { //throws NoSuchElementException
//todo
if (!hasNext()) {
throw new NoSuchElementException();
}
Integer res = next;
while (iterator.hasNext()) {
Integer next = iterator.next();
if (next != null && next > 0) {
this.next = next;
break;
}
}
if (!iterator.hasNext()) {
next = null;
}
return res;
}
@Override
public void remove() {
throw new UnsupportedOperationException();
}
public static void main(String[] args) {
Iterator<Integer> intIter = Arrays.asList(new Integer[] {null, -1, 2, null, 15, -4, 50, null}).iterator();
Iterator<Integer> iter = new PositiveIntegerIterator(intIter);
// //multiple hasNext() calls succeed
// for (int i = 0; i < 100; i++) {
// assert iter.hasNext();
// }
while (iter.hasNext()) {
System.out.println(iter.next());
}
/*//values are correct
iter.hasNext();
iter.next() == 2;
//no hasNext() call...
assert iter.next() == 15;
assert iter.hasNext();
assert iter.next() == 50;
assert iter.hasNext() == false;*/
}
}