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package me.aifaq.commons.lang;
import com.google.common.base.Preconditions;
import me.aifaq.commons.lang.base.Function;
import me.aifaq.commons.lang.base.MappableFunction;
import me.aifaq.commons.lang.base.OperableFunction;
import org.apache.commons.collections4.CollectionUtils;
import org.apache.commons.lang3.StringUtils;
import java.math.BigDecimal;
import java.util.*;
/**
* @author Wang Wei [[email protected]]
* @since 10:10 2017/5/17
*/
public class CollectionUtil {
/**
* 如果对象为null，返回0
*
* @param object
* @return
*/
public static int size(Object object) {
if (object == null) {
return 0;
}
return CollectionUtils.size(object);
}
/**
* 自定义函数转换得到List
*
* @param sources 源数据集合
* @param function 转换函数
* @param 源数据类型
* @param 目标数据类型
* @return
*/
public static List transformList(Collection sources, Function function) {
Preconditions.checkNotNull(function);
if (CollectionUtils.isEmpty(sources)) {
return new ArrayList<>(0);
}
final List targets = new ArrayList<>(sources.size());
for (S source : sources) {
if (source == null && function.skipIfNull()) {
continue;
}
final T target = function.apply(source);
if (target == null && function.skipIfApplyNull()) {
continue;
}
targets.add(target);
}
return targets;
}
/**
* 自定义函数转换得到Set
*
* @param sources 源数据集合
* @param function 转换函数
* @param 源数据类型
* @param 目标数据类型
* @return
*/
public static Set transformSet(Collection sources, Function function) {
Preconditions.checkNotNull(function);
if (CollectionUtils.isEmpty(sources)) {
return new HashSet<>();
}
final Set targets = new HashSet<>();
for (S source : sources) {
if (source == null && function.skipIfNull()) {
continue;
}
final T target = function.apply(source);
if (target == null && function.skipIfApplyNull()) {
continue;
}
targets.add(target);
}
return targets;
}
/**
* 自定义函数转换得到Map
*
* @param sources 源数据集合
* @param function 转换函数
* @param 源数据类型
* @param 目标数据类型
* @return
*/
public static Map transformMap(Collection sources, MappableFunction function) {
Preconditions.checkNotNull(function);
if (CollectionUtils.isEmpty(sources)) {
return new HashMap<>();
}
final Map targets = new HashMap<>();
for (S source : sources) {
if (source == null && function.skipIfNull()) {
continue;
}
final Map.Entry entry = function.apply(source);
if (entry == null && function.skipIfApplyNull()) {
continue;
}
targets.put(entry.getKey(), entry.getValue());
}
return targets;
}
/**
* 求和
*
* @param sources 源数据集合
* @param function 转换函数
* @param 源数据类型
* @return
*/
public static BigDecimal sum(Collection sources, OperableFunction function) {
Preconditions.checkNotNull(function);
if (CollectionUtils.isEmpty(sources)) {
return BigDecimal.ZERO;
}
BigDecimal result = BigDecimal.ZERO;
for (S source : sources) {
if (source == null && function.skipIfNull()) {
continue;
}
final BigDecimal target = function.apply(source);
if (target == null && function.skipIfApplyNull()) {
continue;
}
result = result.add(target);
}
return result;
}
/**
* @see #sum(Collection, OperableFunction)
*/
public static BigDecimal sum(Collection sources) {
return sum(sources, new OperableFunction() {
@Override
public BigDecimal apply(BigDecimal source) {
return source;
}
});
}
/**
* 是否存在null值
*
* @param collection
* @return
*/
public static boolean hasNull(Collection collection) {
if (collection == null) {
return true;
}
for (Object object : collection) {
if (object == null) {
return true;
}
}
return false;
}
/**
* 拼接字符串
*
* @param collection 目标集合
* @param separator 拼接字符
* @param ignoreNull 是否忽略null值
* @return
*/
public static String join(Collection collection, Object separator, boolean ignoreNull) {
if (CollectionUtils.isEmpty(collection)) {
return StringUtils.EMPTY;
}
final StringBuilder result = new StringBuilder();
int mark = 0;
for (Object object : collection) {
if (object == null && ignoreNull) {
continue;
}
if (mark++ > 0) {
result.append(separator);
}
result.append(object);
}
return result.toString();
}
/**
* @see #join(Collection, Object, boolean)
*/
public static String join(Collection collection, Object seperator) {
return join(collection, seperator, true);
}
/**
* @see #join(Collection, Object, boolean)
*/
public static String join(Collection collection) {
return join(collection, StringUtil.COMMA, true);
}
/**
* 拼接字符串
*
* @param collection 目标集合
* @param separator 拼接字符
* @param nullReplaced null被替换的值
* @return
*/
public static String join(Collection collection, Object separator, Object nullReplaced) {
if (CollectionUtils.isEmpty(collection)) {
return StringUtils.EMPTY;
}
final StringBuilder result = new StringBuilder();
int mark = 0;
for (Object object : collection) {
if (mark++ > 0) {
result.append(separator);
}
result.append(object == null ? nullReplaced : object);
}
return result.toString();
}
/**
* 添加元素至集合中
*
* @param target
* @param source
* @param
* @return
*/
public static Collection addAll(Collection target, Iterable source) {
Preconditions.checkNotNull(target);
if (source == null) {
return target;
}
final Iterator iterator = source.iterator();
while (iterator.hasNext()) {
target.add(iterator.next());
}
return target;
}
/**
* 获取集合的首元素
*
* @param collection
* @param
* @return
*/
public static T first(Collection collection) {
if (CollectionUtils.isEmpty(collection)) {
return null;
}
if (collection instanceof LinkedList) {
return ((LinkedList) collection).getFirst();
} else if (collection instanceof List) {
return ((List) collection).get(0);
}
final Iterator iterator = collection.iterator();
return iterator.hasNext() ? iterator.next() : null;
}
/**
* 获取集合的尾元素
*
* @param collection
* @param
* @return
*/
public static T last(Collection collection) {
if (CollectionUtils.isEmpty(collection)) {
return null;
}
if (collection instanceof LinkedList) {
return ((LinkedList) collection).getLast();
} else if (collection instanceof List) {
return ((List) collection).get(collection.size() - 1);
}
final Iterator iterator = collection.iterator();
T last = null;
do {
if (iterator.hasNext()) {
last = iterator.next();
} else {
return last;
}
} while (true);
}
/**
* 创建{@link ArrayList}对象，初始容量为0
*
* @param
* @return
*/
public static ArrayList newEmptyArrayList() {
return new ArrayList<>(0);
}
/**
* 创建{@link HashSet}对象，初始容量为0
*
* @param
* @return
*/
public static HashSet newEmptyHashSet() {
return new HashSet<>(0);
}
}
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