public class LimitedArrayList<T> extends ArrayList<T>{
private int limit;
public LimitedArrayList(int limit){
this.limit = limit;
}
@Override
public void add(T item){
if (this.size() > limit)
throw new ListTooLargeException();
super.add(item);
}
// ... similarly for other methods that may add new elements ...
import java.util.ArrayList;
public class FixedSizeList<T> extends ArrayList<T> {
public FixedSizeList(int capacity) {
super(capacity);
for (int i = 0; i < capacity; i++) {
super.add(null);
}
}
public FixedSizeList(T[] initialElements) {
super(initialElements.length);
for (T loopElement : initialElements) {
super.add(loopElement);
}
}
@Override
public void clear() {
throw new UnsupportedOperationException("Elements may not be cleared from a fixed size List.");
}
@Override
public boolean add(T o) {
throw new UnsupportedOperationException("Elements may not be added to a fixed size List, use set() instead.");
}
@Override
public void add(int index, T element) {
throw new UnsupportedOperationException("Elements may not be added to a fixed size List, use set() instead.");
}
@Override
public T remove(int index) {
throw new UnsupportedOperationException("Elements may not be removed from a fixed size List.");
}
@Override
public boolean remove(Object o) {
throw new UnsupportedOperationException("Elements may not be removed from a fixed size List.");
}
@Override
protected void removeRange(int fromIndex, int toIndex) {
throw new UnsupportedOperationException("Elements may not be removed from a fixed size List.");
}
}
List<String> s = newFixedSizeList(3); // All elements are initialized to null
s.set(0, "zero");
s.add("three"); // throws java.lang.UnsupportedOperationException
static class FixedSizeCircularReference<T> {
T[] entries
FixedSizeCircularReference(int size) {
this.entries = new Object[size] as T[]
this.size = size
}
int cur = 0
int size
void add(T entry) {
entries[cur++] = entry
if (cur >= size) {
cur = 0
}
}
List<T> asList() {
List<T> list = new ArrayList<>()
int oldest = (cur == size - 1) ? 0 : cur
for (int i = 0; i < this.entries.length; i++) {
def e = this.entries[oldest + i < size ? oldest + i : oldest + i - size]
if (e) list.add(e)
}
return list
}
}
FixedSizeCircularReference<String> latestEntries = new FixedSizeCircularReference(100)
latestEntries.add('message 1')
// .....
latestEntries.add('message 1000')
latestEntries.asList() //Returns list of '100' messages