程序编写和修改
基本计算器应用
你需要开发一个简单的Java桌面计算器应用。这个计算器应该具有以下基本功能：
用户可以输入数字和运算符（+、-、*、/）来执行基本的算术运算。
计算器应该能够显示输入和结果，以便用户可以看到他们的操作。
用户应该能够进行连续运算，例如输入"5 + 3 * 2"，并正确计算结果。
应用程序应该包含一个“清除”按钮，以允许用户清除输入并重新开始。
改进计算器应用
在基本计算器应用的基础上，你需要实现以下改进功能：
添加一个小数点按钮，使用户能够输入小数。
添加一个平方根按钮，使用户能够计算输入数字的平方根。
添加一个百分比按钮，使用户能够将当前数字转换为百分比。
实现一个“回退”按钮，允许用户删除他们最后输入的字符。
标准答案：
import javax.swing.*;
import java.awt.*;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
public class CalculatorApp extends JFrame implements ActionListener {
private JTextField textField;
private String input = "";
public CalculatorApp() {
// 创建界面和组件
setTitle("简易计算器");
setSize(300, 400);
setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
setLayout(new BorderLayout());
textField = new JTextField();
textField.setFont(new Font("Arial", Font.PLAIN, 24));
textField.setHorizontalAlignment(JTextField.RIGHT);
add(textField, BorderLayout.NORTH);
JPanel buttonPanel = new JPanel();
buttonPanel.setLayout(new GridLayout(5, 4));
// 创建按钮并添加到面板上
String[] buttonLabels = {
"7", "8", "9", "/",
"4", "5", "6", "*",
"1", "2", "3", "-",
"0", ".", "=", "+"
};
for (String label : buttonLabels) {
JButton button = new JButton(label);
button.setFont(new Font("Arial", Font.PLAIN, 18));
button.addActionListener(this);
buttonPanel.add(button);
}
add(buttonPanel, BorderLayout.CENTER);
JButton clearButton = new JButton("清除");
clearButton.setFont(new Font("Arial", Font.PLAIN, 18));
clearButton.addActionListener(this);
add(clearButton, BorderLayout.SOUTH);
}
@Override
public void actionPerformed(ActionEvent e) {
String command = e.getActionCommand();
if (command.equals("=")) {
try {
double result = evaluate(input);
textField.setText(String.valueOf(result));
} catch (Exception ex) {
textField.setText("错误");
}
input = "";
} else if (command.equals("清除")) {
input = "";
textField.setText("");
} else {
input += command;
textField.setText(input);
}
}
private double evaluate(String expression) throws Exception {
// 实现基本计算器逻辑
// 这里需要你实现计算逻辑
return 0.0;
}
public static void main(String[] args) {
SwingUtilities.invokeLater(() -> {
CalculatorApp calculator = new CalculatorApp();
calculator.setVisible(true);
});
}
}
改进程序答案：
改进计算器应用的实现将包括添加小数点、平方根、百分比和回退功能的代码。以下是一个简要的示例：
// 在 CalculatorApp 类中添加以下方法和代码
private boolean isOperator(char c) {
return c == '+' || c == '-' || c == '*' || c == '/';
}
private double calculate(double operand1, char operator, double operand2) {
switch (operator) {
case '+':
return operand1 + operand2;
case '-':
return operand1 - operand2;
case '*':
return operand1 * operand2;
case '/':
if (operand2 != 0) {
return operand1 / operand2;
} else {
throw new ArithmeticException("除数不能为零");
}
default:
throw new IllegalArgumentException("无效的运算符: " + operator);
}
}
private double evaluate(String expression) throws Exception {
// 使用栈来计算表达式
Stack<Double> operandStack = new Stack<>();
Stack<Character> operatorStack = new Stack<>();
int index = 0;
while (index < expression.length()) {
char currentChar = expression.charAt(index);
if (Character.isDigit(currentChar) || currentChar == '.') {
StringBuilder operandBuilder = new StringBuilder();
while (index < expression.length() && (Character.isDigit(expression.charAt(index)) || expression.charAt(index) == '.')) {
operandBuilder.append(expression.charAt(index));
index++;
}
double operand = Double.parseDouble(operandBuilder.toString());
operandStack.push(operand);
} else if (isOperator(currentChar)) {
while (!operatorStack.isEmpty() && isOperator(operatorStack.peek()) && getPrecedence(currentChar) <= getPrecedence(operatorStack.peek())) {
double operand2 = operandStack.pop();
double operand1 = operandStack.pop();
char operator = operatorStack.pop();
double result = calculate(operand1, operator, operand2);
operandStack.push(result);
}
operatorStack.push(currentChar);
index++;
} else if (currentChar == '(') {
operatorStack.push(currentChar);
index++;
} else if (currentChar == ')') {
while (!operatorStack.isEmpty() && operatorStack.peek() != '(') {
double operand2 = operandStack.pop();
double operand1 = operandStack.pop();
char operator = operatorStack.pop();
double result = calculate(operand1, operator, operand2);
operandStack.push(result);
}
if (!operatorStack.isEmpty() && operatorStack.peek() == '(') {
operatorStack.pop();
} else {
throw new IllegalArgumentException("括号不匹配");
}
index++;
} else {
throw new IllegalArgumentException("无效字符: " + currentChar);
}
}
while (!operatorStack.isEmpty()) {
if (operatorStack.peek() == '(') {
throw new IllegalArgumentException("括号不匹配");
}
double operand2 = operandStack.pop();
double operand1 = operandStack.pop();
char operator = operatorStack.pop();
double result = calculate(operand1, operator, operand2);
operandStack.push(result);
}
if (operandStack.size() == 1 && operatorStack.isEmpty()) {
return operandStack.pop();
} else {
throw new IllegalArgumentException("无效表达式");
}
}
private int getPrecedence(char operator) {
if (operator == '+' || operator == '-') {
return 1;
} else if (operator == '*' || operator == '/') {
return 2;
} else {
return 0;
}
}
功能调试
下面是一个简单的学生信息管理系统的Java桌面应用代码，你可以在此基础上进行功能调试与验证。随后，我将提供一个包含五个问题的上机考核题目以及标准答案。
public class Student {
private String studentNumber;
private String name;
private double score;
public Student(String studentNumber, String name, double score) {
this.studentNumber = studentNumber;
this.name = name;
this.score = score;
}
public String getStudentNumber() {
return studentNumber;
}
public String getName() {
return name;
}
public double getScore() {
return score;
}
@Override
public String toString() {
return "Student [studentNumber=" + studentNumber + ", name=" + name + ", score=" + score + "]";
}
}
学生信息管理系统类 (StudentManager.java):
import java.util.ArrayList;
import java.util.List;
public class StudentManager {
private List<Student> students;
public StudentManager() {
students = new ArrayList<>();
}
public void addStudent(Student student) {
students.add(student);
}
public void deleteStudentByStudentNumber(String studentNumber) {
students.removeIf(student -> student.getStudentNumber().equals(studentNumber));
}
public List<Student> getAllStudents() {
return students;
}
public void sortStudentsByScore(boolean ascending) {
students.sort((s1, s2) -> {
if (ascending) {
return Double.compare(s1.getScore(), s2.getScore());
} else {
return Double.compare(s2.getScore(), s1.getScore());
}
});
}
public List<Student> searchStudentsByName(String name) {
List<Student> foundStudents = new ArrayList<>();
for (Student student : students) {
if (student.getName().equalsIgnoreCase(name)) {
foundStudents.add(student);
}
}
return foundStudents;
}
}
标准答案示例：
验证添加学生信息功能：
Studentstudent=newStudent("S12345","Alice",88.5);
studentManager.addStudent(student);
List allStudents = studentManager.getAllStudents();System.out.println("所有学生信息："+ allStudents);
验证删除学生信息功能：
studentManager.deleteStudentByStudentNumber("S12345");
List allStudents = studentManager.getAllStudents();
System.out.println("所有学生信息："+ allStudents);
验证按成绩排序功能：
studentManager.sortStudentsByScore(true);
List sortedStudents = studentManager.getAllStudents();
System.out.println("按成绩升序排序后的学生信息："+ sortedStudents);
验证按姓名查找功能：
List foundStudents = studentManager.searchStudentsByName("Alice");
System.out.println("查找到的学生信息："+ foundStudents);
