从字符串路径列表构造树结构

遵循可访问树的幼稚实现的实现：

class Tree<T> implements Visitable<T> {    // NB: linkedHashSet preserves insertion order    private final Set<Tree> children = new linkedHashSet<Tree>();    private final T data;    Tree(T data) {        this.data = data;    }    void accept(Visitor<T> visitor) {        visitor.visitData(this, data);        for (Tree child : children) { Visitor<T> childVisitor = visitor.visitTree(child); child.accept(childVisitor);        }    }    Tree child(T data) {        for (Tree child: children ) { if (child.data.equals(data)) {     return child; }        }        return child(new Tree(data));    }    Tree child(Tree<T> child) {        children.add(child);        return child;    }}

访客模式的界面：

interface Visitor<T> {    Visitor<T> visitTree(Tree<T> tree);    void visitData(Tree<T> parent, T data);}interface Visitable<T> {    void accept(Visitor<T> visitor);}

访客模式的示例实现：

class PrintIndentedVisitor implements Visitor<String> {    private final int indent;    PrintIndentedVisitor(int indent) {        this.indent = indent;    }    Visitor<String> visitTree(Tree<String> tree) {        return new IndentVisitor(indent + 2);    }    void visitData(Tree<String> parent, String data) {        for (int i = 0; i < indent; i++) { // TODO: naive implementation System.out.print(" ");        }        System.out.println(data);    }}

最后（!!!）一个简单的测试用例：

    Tree<String> forest = new Tree<String>("forest");    Tree<String> current = forest;    for (String tree : Arrays.asList("x1/x2/x3", "x1/x2/x4", "x1/x5")) {        Tree<String> root = current;        for (String data: tree.split("/")) { current = current.child(data);        }        current = root;    }    forest.accept(new PrintIndentedVisitor(0));

输出：

森林  x1    2倍      3倍      4倍    5倍