Question

package StreetKing;

import java.awt.Color;

public class TrffcLgt {

    public static void main(String[] args) {
        // TODO Auto-generated method stub
        /**
        * This class represents a simple implementation of a stoplight.
        * The client can determine the current state of the stoplight by
        * calling stoplight.getState() and change it to the next color
        * in the sequence (GREEN -> YELLOW -> RED -> GREEN) by calling
        * stoplight.advance().
        */
        public class Stoplight {
        /** Constant indicating the color GREEN */
        public static final Color GREEN = Color.GREEN;
        /** Constant indicating the color YELLOW */
        public static final Color YELLOW = Color.YELLOW;
        /** Constant indicating the color RED */
        public static final Color RED = Color.RED;
        /**
        * Creates a new Stoplight object, which is initially GREEN.
        */
        public Stoplight() {
            state = 0;
        }

        /**
        * Returns the current state of the stoplight.
        * @return The state of the stoplight (GREEN, YELLOW, or RED)
        */
        public Color getState() {
            switch (state) {
                case 0: return GREEN;
                case 1: return YELLOW;
                case 2: return RED;
                default: return null; /* Can't occur but required by Java */
             }
        }

        /**
        * Advances the stoplight to the next state.
        */
        public void advance() {
            state = (state + 1) % 3;
        }

        /* Private instance variable */
        private int state;
        }
    }

}

获取错误消息＆＃34;本地类Stoplight的非法修饰符;只允许抽象或最终＃34;应该解决这个问题的方法是什么？

Answer 1

问题在于您不恰当地尝试在方法中声明类Stoplight （您的main方法）。

这在技术上是允许的（是的！它是本地类）但是如果在此上下文中声明了一个类，则不能将其声明为public。（考虑一下。类声明直观地仅在方法体内的范围内。因此将其声明为public毫无意义。）

话虽如此，可能在这里做的不是正确的事。更好的解决方案是将Stoplight类移动到单独的文件中，或将其移动到（名义上命名的）TrrfcLgt类中，以便它是嵌套类。（如果您执行后者，请将其更改为static ...）

Answer 2

将Stoplight类定义移到main方法之外。

我是java的新手。获取下面列出的错误消息

2 个答案: