a) Many GUI applications have metres that indicate the progress made so far towards completing an activity as a percentage of the anticipated total activity. Write a program to display a progress metre as follows. The metre consists of a window with a column of 11 labels. The first 10 labels indicate progress steps of 10% and are initially red. The bottom label shows the amount of activity remaining as a textual percentage, and is initially set to “0%”. (Correct layout: 0.25P, Class extends JFrame: 0.25P, Class follows OOP principles: 0.25P, Global set-up in main method: 0.25P)2 b) Create functionality to simulate steps of 10% progress. For this the user repeatedly presses return on the console inside Eclipse (use a Scanner object for this). Every time, the top-most red label is changed to green and the progress label value is incremented by 10 until that value is 100%. Make sure that no errors occur if the user tries to go past 100%.怎么做？

以下是实现上述功能的 Java 代码：

import javax.swing.*;
import java.awt.*;
import java.util.Scanner;

public class ProgressMeter extends JFrame {
    private JLabel[] steps;
    private JLabel progressLabel;
    private int progress;

    public ProgressMeter() {
        setTitle("Progress Meter");
        setSize(200, 300);
        setLocationRelativeTo(null);
        setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        setLayout(new GridLayout(11, 1));

        // Create the steps labels
        steps = new JLabel[10];
        for (int i = 0; i < 10; i++) {
            JLabel stepLabel = new JLabel((i + 1) * 10 + "%");
            stepLabel.setForeground(Color.RED);
            add(stepLabel);
            steps[i] = stepLabel;
        }

        // Create the progress label
        progressLabel = new JLabel(progress + "%");
        progressLabel.setForeground(Color.BLACK);
        add(progressLabel);

        setVisible(true);
    }

    public void updateProgress() {
        if (progress < 100) {
            steps[progress / 10].setForeground(Color.GREEN);
            progress += 10;
            progressLabel.setText(progress + "%");
        }
    }

    public static void main(String[] args) {
        ProgressMeter meter = new ProgressMeter();
        Scanner scanner = new Scanner(System.in);

        while (meter.progress < 100) {
            System.out.print("Press Enter to make progress: ");
            scanner.nextLine();
            meter.updateProgress();
        }
    }
}

这个程序使用了 Java 的 Swing 库创建了一个窗口，包含一个由 11 个标签组成的表，其中前 10 个标签表示进度的 10％ 步骤，初始颜色为红色，最后一个标签用于显示剩余的活动量，初始值为 “0％”。程序的主要逻辑在 `updateProgress()` 方法中，它将更新进度，并将相应的标签从红色更改为绿色。在主方法中，我们使用 Scanner 对象读取用户的输入，并在每次输入时调用 `updateProgress()` 方法来更新进度。