com.googlecode.common.client.util.CollectionsUtil Maven / Gradle / Ivy
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package com.googlecode.common.client.util;
import java.util.ArrayList;
import java.util.List;
public final class CollectionsUtil {
public interface Predicate {
public boolean predicate(P object);
}
public interface Function {
public R exec(T object);
}
private CollectionsUtil() {
}
public static List addToList(List list, T data) {
if (list == null) {
list = new ArrayList();
}
list.add(data);
return list;
}
public static List addAllToList(List list, List data) {
if (list == null) {
list = new ArrayList();
}
list.addAll(data);
return list;
}
/**
* Selects first element which satisfies predicate
*/
public static T first(List list,
Predicate predicate) {
for (T e : list) {
if (predicate.predicate(e)) {
return e;
}
}
return null;
}
/**
* Tests whether a predicate holds for some of the elements of the list
*/
public static boolean exists(List list,
Predicate predicate) {
return first(list, predicate) != null;
}
/**
* Selects all elements which satisfy a predicate
*
* @return new {@code List} containing filtered elements
*/
public static List filter(List list,
Predicate predicate) {
List filteredList = new ArrayList();
for (T e : list) {
if (predicate.predicate(e)) {
filteredList.add(e);
}
}
return filteredList;
}
/**
* Builds a new List by applying a function to all elements of this list
* @return new {@code List} containing elements returned by {@code func}
*/
public static List map(List list, Function func) {
List result = new ArrayList();
for (T e : list) {
result.add(func.exec(e));
}
return result;
}
}