/
IteratorUtils.java
124 lines (103 loc) · 2.2 KB
/
IteratorUtils.java
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package net.stencilproject.template;
import java.lang.reflect.Array;
import java.util.Iterator;
import java.util.Map;
import java.util.Map.Entry;
class IteratorUtils {
/**
* Represents the null iterator - one that has no values.
*/
public static final Iterator<Object> NULL_ITERATOR = new Iterator<Object>() {
@Override
public boolean hasNext() {
return false;
}
@Override
public Object next() {
return null;
}
@Override
public void remove() {
}
};
/**
* Limits an iterator to a given count.
*/
public static <T> Iterator<T> limitIterator(final Iterator<T> it, final long limit) {
return new Iterator<T>() {
long left = limit;
@Override
public void remove() {
}
@Override
public T next() {
left--;
return it.next();
}
@Override
public boolean hasNext() {
return left > 0 && it.hasNext();
}
};
}
/**
* Converts a string to an iterator of characters.
*/
public static Iterator<Character> toIterator(final String value) {
return new Iterator<Character>() {
int index = 0;
@Override
public boolean hasNext() {
return index < value.length();
}
@Override
public Character next() {
return value.charAt(index++);
}
@Override
public void remove() {
}
};
}
/**
* Converts an array to an iterator of objects.
*/
public static Iterator<Object> toIteratorArray(final Object array) {
final int length = Array.getLength(array);
return new Iterator<Object>() {
int index = 0;
@Override
public boolean hasNext() {
return index < length;
}
@Override
public Object next() {
return Array.get(array, index++);
}
@Override
public void remove() {
}
};
}
/**
* Wraps a map iterator with an iterator that returns tuples of [key,
* value].
*/
public static Iterator<?> toIterator(Map<?, ?> o) {
final Iterator<?> it = o.entrySet().iterator();
return new Iterator<Object>() {
@Override
public boolean hasNext() {
return it.hasNext();
}
@Override
public Object next() {
Map.Entry<?, ?> entry = (Entry<?, ?>) it.next();
return new Object[] { entry.getKey(), entry.getValue() };
}
@Override
public void remove() {
}
};
}
}