Spring IoC：把对象关系交给容器管理

import java.util.*;
public class Main {
    static List<String> order(Map<String,List<String>> graph) {
        List<String> result = new ArrayList<>();
        Map<String,Integer> color = new HashMap<>();
        Deque<String> path = new ArrayDeque<>();
        // 排序只保证示例输出稳定，不模拟真实容器创建顺序。
        for (String name : new TreeSet<>(graph.keySet()))
            visit(name, graph, color, path, result);
        return List.copyOf(result);
    }
    static void visit(String name, Map<String,List<String>> graph,
            Map<String,Integer> color, Deque<String> path, List<String> result) {
        if (!graph.containsKey(name)) throw new IllegalArgumentException("missing: " + name);
        int state = color.getOrDefault(name, 0);
        if (state == 2) return; // 已完成的共享依赖只输出一次。
        if (state == 1) throw new IllegalArgumentException("cycle: " + path + " -> " + name);
        color.put(name, 1);
        path.addLast(name);
        for (String dependency : graph.get(name))
            visit(dependency, graph, color, path, result);
        path.removeLast();
        // 依赖全部完成后才允许发布当前节点。
        color.put(name, 2);
        result.add(name);
    }
    static void eq(Object expected, Object actual) {
        if (!Objects.equals(expected, actual)) throw new AssertionError(actual);
    }
    static void fails(String text, Runnable test) {
        try { test.run(); throw new AssertionError("expected failure"); }
        catch (IllegalArgumentException e) {
            if (!e.getMessage().contains(text)) throw new AssertionError(e);
        }
    }
    public static void main(String[] args) {
        eq(List.of(), order(Map.of()));
        eq(List.of("mapper","service","controller"), order(Map.of(
            "controller",List.of("service"),"service",List.of("mapper"),"mapper",List.of())));
        eq(List.of("d","b","c","a"), order(Map.of(
            "a",List.of("b","c"),"b",List.of("d"),"c",List.of("d"),"d",List.of())));
        fails("missing", () -> order(Map.of("a",List.of("b"))));
        fails("cycle", () -> order(Map.of("a",List.of("b"),"b",List.of("a"))));
        fails("cycle", () -> order(Map.of("a",List.of("a"))));
        System.out.println("PASS 6 dependency graph tests");
    }
}