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larry1001/CollectionUtils.java

Last active March 8, 2019 02:06
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java Collections操作封装类
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CollectionUtils.java
import java.util.*;
/**
* 类名称:CollectionUtils.java<br>
* 类描述:集合工具类
*/
public final class CollectionUtils {
public static boolean isArray(Object obj) {
return (obj != null && obj.getClass().isArray());
}
public static <T> boolean isEmpty(T[] array) {
return array == null || array.length == 0;
}
public static <T> boolean isNotEmpty(T[] array) {
return !isEmpty(array);
}
public static <T> boolean isEmpty(Collection<T> collection) {
return collection == null || collection.size() == 0;
}
public static <T> boolean isNotEmpty(Collection<T> collection) {
return !isEmpty(collection);
}
public static boolean isEmpty(Map map) {
return map == null || map.isEmpty();
}
public static boolean isNotEmpty(Map map) {
return !isEmpty(map);
}
public static <T> String toStr(Collection<T> collection) {
return toStr(collection, ",");
}
public static <T> String toStr(Collection<T> collection, String split) {
return toStr(collection.toArray(), split);
}
public static String toStr(Object[] array) {
return toStr(array, ",");
}
public static String toStr(Object[] array, String split) {
if (isEmpty(array)) {
return CommonUtils.EMPTY;
}
StringBuilder sbd = new StringBuilder();
for (int i = 0; i < array.length; i++) {
sbd.append(array[i]);
if (i + 1 != array.length) {
sbd.append(split);
}
}
return sbd.toString();
}
@SuppressWarnings("unchecked")
public static <T> List<T> lists(T... values) {
return new ArrayList<T>(java.util.Arrays.asList(values));
}
@SuppressWarnings("unchecked")
public static <T> List<T> linkedLists(T... values) {
return new LinkedList<T>(java.util.Arrays.asList(values));
}
@SuppressWarnings("unchecked")
public static <T> Set<T> sets(T... sets) {
return new HashSet<T>(java.util.Arrays.asList(sets));
}
@SuppressWarnings("unchecked")
public static <T> Set<T> linkedSets(T... sets) {
return new LinkedHashSet<T>(java.util.Arrays.asList(sets));
}
public static <K, V> HashMap<K, V> newHashMap() {
return new HashMap<K, V>();
}
public static <K, V> HashMap<K, V> newLinkedHashMap() {
return new LinkedHashMap<K, V>();
}
@SuppressWarnings("unchecked")
public static <K, V> HashMap<K, V> maps(Object... keysAndValues) {
return (HashMap<K, V>) maps(newHashMap(), keysAndValues);
}
@SuppressWarnings("unchecked")
private static <K, V> Map<K, V> maps(Map<K, V> result, Object... keysAndValues) {
if (isNotEmpty(keysAndValues)) {
for (int i = 0; i < keysAndValues.length; i += 2) {
if (keysAndValues.length > (i + 1)) {
result.put((K) keysAndValues[i], (V) keysAndValues[i + 1]);
}
}
}
return result;
}
@SuppressWarnings("unchecked")
public static <K, V> LinkedHashMap<K, V> linkedMaps(Object... keysAndValues) {
return (LinkedHashMap<K, V>) maps(newLinkedHashMap(), keysAndValues);
}
public static <T> T first(Collection<T> collection) {
return isEmpty(collection) ? null : collection.iterator().next();
}
public static <T> T last(Collection<T> collection) {
if (isEmpty(collection)) {
return null;
}
if (collection instanceof List) {
List<T> list = (List<T>) collection;
return list.get(list.size() - 1);
}
Iterator<T> iterator = collection.iterator();
while (true) {
T current = iterator.next();
if (!iterator.hasNext()) {
return current;
}
}
}
}
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