如何更改 Java 中的枚举值？

Question

我有一个枚举 Direction，它显示了合法的步行方向。使用辅助方法 turnLeft 我想改变被调用的枚举变量的值，但是它不起作用：方法调用后枚举变量的值direction相同

enum Direction{    
    UP, RIGHT, DOWN, LEFT
}

private Direction direction = Direction.DOWN;

public void turnLeft(Direction direction) {

    switch(direction) {
        case UP: this.direction = Direction.LEFT; break;
        case RIGHT: this.direction = Direction.UP; break;
        case DOWN: this.direction = Direction.RIGHT; break;
        case LEFT: this.direction = Direction.DOWN; break;
    }

}

我做错了什么？

Answer 1

您可以直接在枚举中添加 turnLeft/turnRight 方法。

enum Direction{
    UP, RIGHT, DOWN, LEFT;

    public Direction turnLeft() {
        switch(this) {
            case UP: return LEFT;
            case RIGHT: return UP;
            case DOWN: return RIGHT;
            default: return DOWN; // if you leave the LEFT case, you still need to return something outside the block on some Java versions
        }
    }
}

然后每当你想转弯时，你可以将“左”值赋给方向变量。

private Direction direction = Direction.DOWN;

public void turnAndPrint() {
    direction = direction.turnLeft();
    System.out.println(direction.name()); // will print RIGHT when called the first time
}

如何更改 Java 中的枚举值？

How to change an enum value in Java?

java

enums

helper

switch-statement