大家好,又见面了,我是你们的朋友全栈君。
package com.ciih.workshop.utils;
import com.baomidou.mybatisplus.core.toolkit.support.SFunction;
import lombok.SneakyThrows;
import java.lang.invoke.SerializedLambda;
import java.lang.reflect.Method;
import java.util.ArrayList;
import java.util.List;
import java.util.Map;
import java.util.function.BiConsumer;
import java.util.function.Function;
import java.util.stream.Collectors;
/**
* 树形工具类-函数版
*
* @author sunziwen
*/
public class TreeUtil {
/**
* Map版本(速度比递归要快很多)
* listToTree
*
* @param target 需转换的数据
* @param getId 主键
* @param getParentId 父id (父id必须和主键相同类型)
* @param getChildren 子集
* @param setChildren 子集
* @return tree
*/
public static <T, R> List<T> listToTree(List<T> target, Function<T, R> getId, Function<T, R> getParentId,
Function<T, List<T>> getChildren, BiConsumer<T, List<T>> setChildren) {
Map<R, T> oldMap = target.stream().collect(Collectors.toMap(getId, T -> T));
List<T> result = new ArrayList<>();
target.forEach(tree -> {
T parent = oldMap.get(getParentId.apply(tree));
if (parent == null) {
result.add(tree);
} else {
List<T> ch = getChildren.apply(parent);
if (ch == null) {
ch = new ArrayList<>();
}
ch.add(tree);
setChildren.accept(parent, ch);
}
});
return result;
}
/**
* @param list 树结构的基础数据集
* @param getIdFn 获取主键的函数
* @param getParentIdFn 获取父节点的函数
* @param getChildrenFn 获取子集的函数
* @param <T> t
* @param <R> r
* @return t
*/
@SneakyThrows
public static <T, R> List<T> treeOut(List<T> list, Function<T, R> getIdFn, Function<T, R> getParentIdFn, SFunction<T, R> getChildrenFn) {
/*所有元素的Id*/
List<Object> ids = list.stream().map(getIdFn).collect(Collectors.toList());
/*查出所有顶级节点*/
List<T> topLevel = list.stream().filter(x -> {
R apply = getParentIdFn.apply(x);
return !ids.contains(apply);
}).collect(Collectors.toList());
return TreeUtil.recursion(topLevel, list, getIdFn, getParentIdFn, getChildrenFn);
}
@SneakyThrows
private static <T, R> List<T> recursion(List<T> superLevel, List<T> list, Function<T, R> getIdFn, Function<T, R> getParentIdFn, SFunction<T, R> getChildrenFn) {
//获取setChildren的Method
Method writeReplaceMethod = getChildrenFn.getClass().getDeclaredMethod("writeReplace");
boolean accessible = writeReplaceMethod.isAccessible();
writeReplaceMethod.setAccessible(true);
SerializedLambda serializedLambda = (SerializedLambda) writeReplaceMethod.invoke(getChildrenFn);
writeReplaceMethod.setAccessible(accessible);
String setMethodName = serializedLambda.getImplMethodName().replaceFirst("g", "s");
Method setMethod = Class.forName(serializedLambda.getImplClass().replace("/", ".")).getDeclaredMethod(setMethodName, List.class);
for (T t : superLevel) {
List<T> children = list.stream().filter(x -> {
R apply = getParentIdFn.apply(x);
R apply1 = getIdFn.apply(t);
return apply.equals(apply1);
}).collect(Collectors.toList());
if (children.size() <= 0) {
continue;
}
List<T> recursion = recursion(children, list, getIdFn, getParentIdFn, getChildrenFn);
setMethod.invoke(t, recursion);
}
return superLevel;
}
}
发布者:全栈程序员栈长,转载请注明出处:https://javaforall.cn/148050.html原文链接:https://javaforall.cn