io.hawt.log.support.LruList Maven / Gradle / Ivy
package io.hawt.log.support;
import java.lang.reflect.Array;
import java.util.Arrays;
/**
* A simple LRU list that stores a fixed size
*/
public class LruList {
private final Class klass;
private final int size;
private T[] elements;
private transient int start = 0;
private transient int end = 0;
private transient boolean full = false;
private final int maxElements;
public LruList(Class klass, int size) {
this.klass = klass;
if (size <= 0) {
throw new IllegalArgumentException("The size must be greater than 0");
}
this.size = size;
elements = createArray(size);
maxElements = elements.length;
}
public synchronized int size() {
int size;
if (end < start) {
size = maxElements - start + end;
} else if (end == start) {
size = (full ? maxElements : 0);
} else {
size = end - start;
}
return size;
}
public synchronized void clear() {
start = 0;
end = 0;
elements = createArray(size);
}
public synchronized void add(T element) {
if (null == element) {
throw new NullPointerException("Attempted to add null object to buffer");
}
if (size() == maxElements) {
Object e = elements[start];
if (null != e) {
elements[start++] = null;
if (start >= maxElements) {
start = 0;
}
full = false;
}
}
elements[end++] = element;
if (end >= maxElements) {
end = 0;
}
if (end == start) {
full = true;
}
}
public synchronized Iterable getElements() {
return getElements(size());
}
public synchronized Iterable getElements(int number) {
int s = size();
int n = Math.min(Math.max(0, number), s);
T[] e = createArray(n);
for (int i = 0; i < n; i++) {
e[i] = elements[(i + s - n + start) % maxElements];
}
return Arrays.asList(e);
}
@SuppressWarnings("unchecked")
private T[] createArray(int size) {
return (T[]) Array.newInstance(klass, size);
}
}