java - java中如何在一个方法中有一个return语句？

Question

我知道如何在一些简单的情况下在方法中返回一个值，但是当一个方法从另一个类返回一个对象时，我不知道如何给出一个变量来存储返回值。具体代码如下:

public Path findPath(Maze maze) {
    Path path = new Path();
    MazePosition initialPos = new MazePosition(0, 0, null);
    Stack<MazePosition> posForExplore = new Stack<MazePosition>();
    MazePosition pos = initialPos;
    MazePosition next;

    posForExplore.push(pos);
    while (!posForExplore.empty()) {
        pos = posForExplore.pop();
        switch (maze.getPosStatus(pos)) {
        case GOAL:
            MazePosition p = pos;
            while (p!=null) {
                path.insertFirst(p.getCoords()[0], p.getCoords()[1]);
                p =p.getFrom();
            }
            return path;
        case VISITED:
            break;
        case OBSTACLE:
            break;
        case OPEN:
            maze.setPosStatus(pos, MazeStatus.VISITED);
            for (Movement mov: DIRS_TO_EXPLORE) {
                next = maze.getNeighbour(pos, mov);
                if (next!=null&&(maze.getPosStatus(next)==MazeStatus.OPEN||maze.getPosStatus(next)==MazeStatus.GOAL)) {
                    posForExplore.push(next);
                }
            }
            break;
        }
    }
    return null;
}

我有一个返回路径并且返回null，那怎么可能只有一个return语句呢。非常感谢!

Answer 1

声明path并将其初始化为null。在插入任何内容之前检查 null 并初始化它(打破循环以触发返回)。最后返回路径。就像，

public Path findPath(Maze maze) {
    Path path = null;
    MazePosition initialPos = new MazePosition(0, 0, null);
    Stack<MazePosition> posForExplore = new Stack<MazePosition>();
    MazePosition pos = initialPos;
    MazePosition next;

    posForExplore.push(pos);
    loop: while (!posForExplore.empty()) {
        pos = posForExplore.pop();
        switch (maze.getPosStatus(pos)) {
        case GOAL:
            MazePosition p = pos;
            while (p != null) {
                if (path == null) {
                    path = new Path();
                }
                path.insertFirst(p.getCoords()[0], p.getCoords()[1]);
                p = p.getFrom();
            }
            break loop;
        case VISITED:
            break;
        case OBSTACLE:
            break;
        case OPEN:
            maze.setPosStatus(pos, MazeStatus.VISITED);
            for (Movement mov : DIRS_TO_EXPLORE) {
                next = maze.getNeighbour(pos, mov);
                if (next != null && (maze.getPosStatus(next) == MazeStatus.OPEN
                        || maze.getPosStatus(next) == MazeStatus.GOAL)) {
                    posForExplore.push(next);
                }
            }
            break;
        }
    }
    return path;
}