请对下面代码进行优化改造；(代码改造题) Java public class TestController { public static void main(String[] args) { //假设下面两个集合分别有六万数据，对下面代码进行优化改良 List<User> largeList = new ArrayList<>(); List<User> smallList = new ArrayList<>(); for (User user : largeList) { for (User test : smallList) { if (user.getId().equals(test.getId())){ System.out.println("业务输出"); } } } } } @Data class User { private Long id; private String name; }

好的，我会根据您的要求回答问题和进行代码优化。关于代码部分，我认为可以使用HashSet来存储smallList中的id，然后只需要遍历一次largeList，将每个用户的id和HashSet中的id进行匹配，如果匹配成功则输出业务信息，这样可以避免嵌套遍历造成的时间复杂度过高。改造后的代码如下： Java public class TestController { public static void main(String[] args) { List<User> largeList = new ArrayList<>(); List<User> smallList = new ArrayList<>(); Set<Long> idSet = new HashSet<>(); for (User user : smallList) { idSet.add(user.getId()); } for (User user : largeList) { if (idSet.contains(user.getId())) { System.out.println("业务输出"); } } } } @Data class User { private Long id; private String name; }

相关问题

帮我优化一下下面的代码： public class TestController { public static void main(String[] args) { String textA = "开发,总监:张三,李四"; String textB = "运维,总监:张三,王五"; String textC = "开发,运维:王五,李四"; List<String> textList = new ArrayList<>(Arrays.asList(textA,textB,textC)); Map<String,Set<String>> result = new HashMap<>(); for (String text : textList) { String[] split = text.split(":"); String[] positions = split[0].split(","); String[] users = split[1].split(","); for (String position : positions) { Set<String> list = result.get(position); if (list == null){ Set<String> userResult = new HashSet<>(); for (String user : users) { userResult.add(user); } result.put(position,userResult); }else { for (String user : users) { list.add(user); } } } } System.out.println(result); } }

以下是代码优化后的结果：

public class TestController {
    public static void main(String[] args) {
        String textA = "开发,总监:张三,李四";
        String textB = "运维,总监:张三,王五";
        String textC = "开发,运维:王五,李四";
        List<String> textList = Arrays.asList(textA, textB, textC);
        Map<String, Set<String>> result = new HashMap<>();
        for (String text : textList) {
            String[] split = text.split(":");
            String[] positions = split[0].split(",");
            String[] users = split[1].split(",");
            for (String position : positions) {
                result.computeIfAbsent(position, k -> new HashSet<>()).addAll(Arrays.asList(users));
            }
        }
        System.out.println(result);
    }
}

优化点如下：

1. 将 `ArrayList` 改为 `Arrays.asList`，利用 `Arrays.asList` 生成的列表可以进行快速的初始化，且不需要额外的内存空间。
2. 将 `if (list == null)` 改为 `result.computeIfAbsent(position, k -> new HashSet<>())`，利用 `computeIfAbsent` 方法可以快速的获得键对应的值，如果值不存在，则会新建一个值并返回。
3. 将 `for (String user : users) { list.add(user); }` 改为 `result.get(position).addAll(Arrays.asList(users));`，利用 `addAll` 方法可以快速地添加一个集合的所有元素。

Also create a ControllerCreate class that extends Controller.The create method takes as arguments the name of a new library user, a number of books (as a string), and an integer representing the role of user to create (where the integer 0 means a lender and the integer 1 means a borrower). The create method of the controller then transforms the book number from a string to an integer (using the Integer.parseInt static method), creates an object from the correct class (based on the role specified by the user input: lender or borrower) and calls the addUser method of the library to add the new user object to the library. • If no exception occurs then the create method of the controller returns the empty string. • If the constructor of the Borrower class throws a NotALenderException then the create method of the controller must catch this exception and return as result the error message from the exception object. • If the parseInt method of the Integer class throws a NumberFormatException (because the user typed something which is not an integer) then the create method of the controller must catch this exception and return as result the error message from the exception object. Modify the run method of the GUI class to add a ViewCreate view that uses a ControllerCreate controller and the same model as before (not a new model!) Do not delete the previous views. Note: if at the end of Question 7 you had manually added to your library (model object) some users for testing, then you must now remove those users from the run method of the anonymous class inside the GUI class. You do not need these test users anymore because you have now a graphical user interface to create new users! Run your GUI and check that you can correctly use the new view to create different users for your library, with different types of roles. • Check that, when you create a new user, the simple view is automatically correctly updated to show the new total number of books borrowed by all users. • Also use the “get book” view to check that the users are correctly created with the correct names and correct number of books. • Also check that trying to create a borrower with a negative number of books correctly shows an error message. Also check that trying to create a user with a number of books which is not an integer correctly shows an error message (do not worry about the content of the error message). After you created a new user, you can also check whether it is a lender or a borrower using the “more book” view to increase the number of books of the user by a big negative number: • if the new user you created is a lender, then increasing the number of books by a big negative value will work and the number of books borrowed by the user will just become a larger value (you can then check that using the “get book” view); • if the new user you created is a borrower, then increasing the number of books by a big negative value will fail with an error message and the number of books borrowed by the user will not change (you can then check that using the “get book” view). 完成符合以上要求的java代码

Model class:

import java.util.ArrayList;

public class Library {
    private ArrayList<User> users;
    private int totalBooksBorrowed;

    public Library() {
        users = new ArrayList<>();
        totalBooksBorrowed = 0;
    }

    public void addUser(User user) {
        users.add(user);
        totalBooksBorrowed += user.getNumberOfBooks();
    }

    public void removeUser(User user) {
        users.remove(user);
        totalBooksBorrowed -= user.getNumberOfBooks();
    }

    public ArrayList<User> getUsers() {
        return users;
    }

    public int getTotalBooksBorrowed() {
        return totalBooksBorrowed;
    }
}

User class:

public abstract class User {
    private String name;
    private int numberOfBooks;

    public User(String name, int numberOfBooks) {
        this.name = name;
        this.numberOfBooks = numberOfBooks;
    }

    public String getName() {
        return name;
    }

    public int getNumberOfBooks() {
        return numberOfBooks;
    }

    public void setNumberOfBooks(int numberOfBooks) {
        this.numberOfBooks = numberOfBooks;
    }

    public abstract boolean isLender();
}

Lender class:

public class Lender extends User {

    public Lender(String name, int numberOfBooks) {
        super(name, numberOfBooks);
    }

    @Override
    public boolean isLender() {
        return true;
    }
}

Borrower class:

public class Borrower extends User {

    public Borrower(String name, int numberOfBooks) throws NotALenderException {
        super(name, numberOfBooks);
        if (numberOfBooks < 0) {
            throw new NotALenderException("A borrower can't have a negative number of books!");
        }
    }

    @Override
    public boolean isLender() {
        return false;
    }
}

NotALenderException class:

public class NotALenderException extends Exception {
    public NotALenderException(String message) {
        super(message);
    }
}

ViewCreate class:

import javax.swing.*;
import java.awt.*;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;

public class ViewCreate extends JPanel implements ActionListener {
    private JTextField nameField = new JTextField(10);
    private JTextField numberOfBooksField = new JTextField(10);
    private JRadioButton lenderButton = new JRadioButton("Lender");
    private JRadioButton borrowerButton = new JRadioButton("Borrower");
    private ButtonGroup roleButtonGroup = new ButtonGroup();
    private JButton createButton = new JButton("Create");

    private ControllerCreate controller;

    public ViewCreate(Model model) {
        this.controller = new ControllerCreate(model, this);

        setLayout(new GridBagLayout());

        roleButtonGroup.add(lenderButton);
        roleButtonGroup.add(borrowerButton);
        lenderButton.setSelected(true);

        GridBagConstraints gc = new GridBagConstraints();
        gc.gridx = 0;
        gc.gridy = 0;
        gc.anchor = GridBagConstraints.LINE_END;
        gc.insets = new Insets(5, 5, 5, 5);
        add(new JLabel("Name: "), gc);

        gc.gridx++;
        gc.anchor = GridBagConstraints.LINE_START;
        add(nameField, gc);

        gc.gridx = 0;
        gc.gridy++;
        gc.anchor = GridBagConstraints.LINE_END;
        add(new JLabel("Number of books: "), gc);

        gc.gridx++;
        gc.anchor = GridBagConstraints.LINE_START;
        add(numberOfBooksField, gc);

        gc.gridx = 0;
        gc.gridy++;
        gc.anchor = GridBagConstraints.LINE_END;
        add(new JLabel("Role: "), gc);

        gc.gridx++;
        gc.anchor = GridBagConstraints.LINE_START;
        add(lenderButton, gc);

        gc.gridx++;
        add(borrowerButton, gc);

        gc.gridx = 1;
        gc.gridy++;
        gc.anchor = GridBagConstraints.LINE_END;
        add(createButton, gc);

        createButton.addActionListener(this);
    }

    @Override
    public void actionPerformed(ActionEvent e) {
        String name = nameField.getText();
        String numberOfBooksString = numberOfBooksField.getText();
        int role = lenderButton.isSelected() ? 0 : 1;

        String result = controller.create(name, numberOfBooksString, role);
        JOptionPane.showMessageDialog(this, result, "Result", JOptionPane.INFORMATION_MESSAGE);
    }
}

ControllerCreate class:

public class ControllerCreate extends Controller {
    private ViewCreate view;

    public ControllerCreate(Model model, ViewCreate view) {
        super(model);
        this.view = view;
    }

    public String create(String name, String numberOfBooksString, int role) {
        try {
            int numberOfBooks = Integer.parseInt(numberOfBooksString);
            User user = null;
            if (role == 0) {
                user = new Lender(name, numberOfBooks);
            } else if (role == 1) {
                user = new Borrower(name, numberOfBooks);
            }
            model.addUser(user);
            view.updateTotalBooksBorrowed();
            return "";
        } catch (NumberFormatException e) {
            return "Invalid number of books!";
        } catch (NotALenderException e) {
            return e.getMessage();
        }
    }
}

GUI class:

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

public class GUI {
    private JFrame frame = new JFrame("Library");
    private Model model = new Library();

    private ViewSimple viewSimple = new ViewSimple(model);
    private ViewGetBook viewGetBook = new ViewGetBook(model);
    private ViewMoreBook viewMoreBook = new ViewMoreBook(model);
    private ViewCreate viewCreate = new ViewCreate(model);

    public GUI() {
        Container cp = frame.getContentPane();
        cp.setLayout(new BorderLayout());
        JTabbedPane tp = new JTabbedPane();
        tp.addTab("Simple", viewSimple);
        tp.addTab("Get book", viewGetBook);
        tp.addTab("More book", viewMoreBook);
        tp.addTab("Create", viewCreate);
        cp.add(tp, BorderLayout.CENTER);
        frame.pack();
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        frame.setVisible(true);

        // Remove test users from model
        model.removeUser(new Lender("John", 2));
        model.removeUser(new Borrower("Mary", 3));
    }

    public static void main(String[] args) {
        SwingUtilities.invokeLater(new Runnable() {
            @Override
            public void run() {
                new GUI();
            }
        });
    }
}