Java实现访问控制矩阵代码

对于Java实现访问控制矩阵代码的问题，我可以提供一些参考代码：

public class AccessControlMatrix {
  private final Set<String> subjects;
  private final Set<String> objects;
  private final Map<String, Map<String, Set<String>>> permissions;

  public AccessControlMatrix(Set<String> subjects, Set<String> objects) {
    this.subjects = subjects;
    this.objects = objects;

    permissions = new HashMap<>();
    for (String subject : subjects) {
      permissions.put(subject, new HashMap<>());
      for (String object : objects) {
        permissions.get(subject).put(object, new HashSet<>());
      }
    }
  }

  public void addPermission(String subject, String object, String permission) {
    if (!subjects.contains(subject)) {
      throw new IllegalArgumentException("Subject not in the matrix.");
    }
    if (!objects.contains(object)) {
      throw new IllegalArgumentException("Object not in the matrix.");
    }
    permissions.get(subject).get(object).add(permission);
  }

  public boolean hasPermission(String subject, String object, String permission) {
    if (!subjects.contains(subject) || !objects.contains(object)) {
      return false;
    }
    return permissions.get(subject).get(object).contains(permission);
  }
}

这是一个基本的访问控制矩阵实现，支持添加权限和查询是否有权限。在实际使用中，需要根据具体的应用场景进行适当的修改和优化。