您可以在java.util.*中使用TreeSet类。它像二叉搜索树一样工作，所以它已经排好序了。TreeSet类实现了Iterable、Collection和Set接口。您可以像使用set一样使用迭代器遍历树。

TreeSet<String> treeSet = new TreeSet<String>();
Iterator<String> it  = treeSet.Iterator();
while(it.hasNext()){
...
}

你可以检查，Java文档和其他的。

public class Tree {
    private List<Tree> leaves = new LinkedList<Tree>();
    private Tree parent = null;
    private String data;

    public Tree(String data, Tree parent) {
        this.data = data;
        this.parent = parent;
    }
}

显然，您可以添加实用工具方法来添加/删除子元素。

例如:

import java.util.ArrayList;
import java.util.List;



/**
 * 
 * @author X2
 *
 * @param <T>
 */
public class HisTree<T> 
{
    private Node<T> root;

    public HisTree(T rootData) 
    {
        root = new Node<T>();
        root.setData(rootData);
        root.setChildren(new ArrayList<Node<T>>());
    }

}

class Node<T> 
{

    private T data;
    private Node<T> parent;
    private List<Node<T>> children;

    public T getData() {
        return data;
    }
    public void setData(T data) {
        this.data = data;
    }
    public Node<T> getParent() {
        return parent;
    }
    public void setParent(Node<T> parent) {
        this.parent = parent;
    }
    public List<Node<T>> getChildren() {
        return children;
    }
    public void setChildren(List<Node<T>> children) {
        this.children = children;
    }
}

与Gareth的答案相同，请检查DefaultMutableTreeNode。它不是一般的，但在其他方面似乎符合要求。即使它在javax中。swing包，它不依赖于任何AWT或swing类。事实上，源代码实际上有注释// ISSUE:这个类不依赖于AWT中的任何东西——移到java.util?

没有回答提到过度简化但有效的代码，所以下面是:

public class TreeNodeArray<T> {
    public T value;
    public final  java.util.List<TreeNodeArray<T>> kids =  new java.util.ArrayList<TreeNodeArray<T>>();
}

我对所有这些方法都有意见。

我使用的是“MappedTreeStructure”实现。这个实现很好地重新组织了树，并且不包含节点的“副本”。

但是没有提供分级方法。

看看那些有问题的输出!

MutableTree<String> tree = new MappedTreeStructure<>();

        tree.add("0", "1");
        tree.add("0", "2");
        tree.add("0", "3");
        tree.add("0", "4");
        tree.add("0", "5");

        tree.add("2", "3");
        tree.add("2", "5");

        tree.add("1", "2");
        tree.add("1", "3");
        tree.add("1", "5");

        System.out.println(
                tree.toString()
        );

哪个输出:(错误)

-  0
  -  1
    -  2
    -  3
    -  5
  -  4

还有这个:(正确)

tree = new MappedTreeStructure<>();

        tree.add("0", "1");
        tree.add("0", "2");
        tree.add("0", "3");
        tree.add("0", "4");
        tree.add("0", "5");

        tree.add("1", "2");
        tree.add("1", "3");
        tree.add("1", "5");

        tree.add("2", "3");
        tree.add("2", "5");

        System.out.println(
                tree.toString()
        );

正确的输出:

-  0
  -  1
    -  2
      -  3
      -  5
  -  4

如此!我创建了另一个实现来欣赏。请给一些建议和反馈!

package util;

import java.util.HashMap;
import java.util.Map;

public class Node<N extends Comparable<N>> {

    public final Map<N, Node<N>> parents = new HashMap<>();
    public final N value;
    public final Map<N, Node<N>> children = new HashMap<>();

    public Node(N value) {
        this.value = value;
    }
}

package util;

import java.util.*;
import java.util.stream.Collectors;

public class HierarchyTree<N extends Comparable<N>> {

    protected final Map<N, Node<N>> nodeList = new HashMap<>();

    public static <T extends Comparable<T>> Node<T> state(Map<T, Node<T>> nodeList, T node) {
        Node<T> tmp = nodeList.getOrDefault(node, new Node<>(node));
        nodeList.putIfAbsent(node, tmp);
        return tmp;
    }

    public static <T extends Comparable<T>> Node<T> state(Map<T, Node<T>> nodeList, Node<T> node) {
        Node<T> tmp = nodeList.getOrDefault(node.value, node);
        nodeList.putIfAbsent(node.value, tmp);
        return tmp;
    }

    public Node<N> state(N child) {
        return state(nodeList, child);
    }

    public Node<N> stateChild(N parent, N child) {
        Node<N> pai = state(parent);
        Node<N> filho = state(child);
        state(pai.children, filho);
        state(filho.parents, pai);
        return filho;
    }

    public List<Node<N>> addChildren(List<N> children) {
        List<Node<N>> retorno = new LinkedList<>();
        for (N child : children) {
            retorno.add(state(child));
        }
        return retorno;
    }

    public List<Node<N>> addChildren(N parent, List<N> children) {
        List<Node<N>> retorno = new LinkedList<>();
        for (N child : children) {
            retorno.add(stateChild(parent, child));
        }
        return retorno;
    }

    public List<Node<N>> addChildren(N parent, N... children) {
        return addChildren(parent, Arrays.asList(children));
    }

    public List<Node<N>> getRoots() {
        return nodeList.values().stream().filter(value -> value.parents.size() == 0).collect(Collectors.toList());
    }

    @Override
    public String toString() {
        return deepPrint("- ");
    }

    public String deepPrint(String prefix) {
        StringBuilder builder = new StringBuilder();
        deepPrint(builder, prefix, "", getRoots());
        return builder.toString();
    }

    protected void deepPrint(StringBuilder builder, String prefix, String sep, List<Node<N>> node) {
        for (Node<N> item : node) {
            builder.append(sep).append(item.value).append("\n");
            deepPrint(builder, prefix, sep + prefix, new ArrayList<>(item.children.values()));
        }
    }

    public SortedMap<Long, Set<N>> tree() {
        SortedMap<Long, Set<N>> tree = new TreeMap<>();
        tree(0L, tree, getRoots());
        return tree;
    }

    protected void tree(Long i, SortedMap<Long, Set<N>> tree, List<Node<N>> roots) {
        for (Node<N> node : roots) {
            Set<N> tmp = tree.getOrDefault(i, new HashSet<>());
            tree.putIfAbsent(i, tmp);
            tmp.add(node.value);
            tree(i + 1L, tree, new ArrayList<>(node.children.values()));
        }
    }

    public void prune() {
        Set<N> nodes = new HashSet<>();
        SortedMap<Long, Set<N>> tree = tree();
        List<Long> treeInverse = tree.keySet().stream().sorted(Comparator.reverseOrder()).collect(Collectors.toList());
        for (Long treeItem : treeInverse) {
            for (N n : tree.get(treeItem)) {
                Map<N, Node<N>> children = nodeList.get(n).children;
                for (N node : nodes) {
                    children.remove(node);
                }
                nodes.addAll(children.keySet());
            }
        }
    }

    public static void main(String[] args) {
        HierarchyTree<Integer> tree = new HierarchyTree<>();
        tree.addChildren(Arrays.asList(1, 2, 3, 4, 5));
        tree.addChildren(1, Arrays.asList(2, 3, 5));
        tree.addChildren(2, Arrays.asList(3, 5));
        tree.prune();
        System.out.println(tree);

        tree = new HierarchyTree<>();
        tree.addChildren(Arrays.asList(1, 2, 3, 4, 5));
        tree.addChildren(2, Arrays.asList(3, 5));
        tree.addChildren(1, Arrays.asList(2, 3, 5));
        tree.prune();
        System.out.println(tree);
    }
}

输出总是正确的:

1
- 2
- - 3
- - 5
4

1
- 2
- - 3
- - 5
4