2022年10月07日Java上机

示例6-1

JBT6201
本例子演示的是异常处理，所以程序会报错
本例子演示的是异常处理，所以程序会报错
本例子演示的是异常处理，所以程序会报错

public class JBT6201 {
    public static void main(String args[]) {
        double num = 1;
        try {
            num = 1 / 0;
        } catch (ArithmeticException e) {
            e.printStackTrace(); 
        }
    }
}

示例6-8

JBT6602

class MoneyException extends Exception {
    private ATM atm;
    private double money;

    MoneyException(ATM atm, double money) {
        this.atm = atm;
        this.money = money;
    }

    public String getExcepMessage() {
        String str = "存款=" + atm.deposit + "<" + "支取=" + money;
        return str;
    }
}

class ATM {
    double deposit;

    ATM(double deposit) {
        this.deposit = deposit;
    }

    public void saveMoney(double money) {
        if (money > 0.0) deposit = deposit + money;
    }

    public void getMoney(double money) throws MoneyException {
        if (deposit < money)
            throw new MoneyException(this, money);
        else {
            System.out.println("取款成功:"+money);
        }
        deposit = deposit - money;
    }

    public void showMoney() {
        System.out.println("存款=" + deposit);
    }
}

public class JBT6602 {
    public static void main(String args[]) {
        ATM atm = new ATM(100);
        try {
            atm.getMoney(299);
        } catch (MoneyException e) {
            System.out.println(e.toString());
            System.out.println(e.getExcepMessage());
        }
    }
}

扩展题

import java.util.HashMap;
import java.util.Map;
import java.util.Scanner;

public class NumberDemo {
    public static void main(String[] args) {
        String[] numberLetter = {"zero", "one", "two", "three", "four", "five", "six", "seven", "eight", "nine"};
        Map<String, Integer> maps = new HashMap();
        for (int i = 0; i < numberLetter.length; i++) {
            maps.put(numberLetter[i], i);
        }
        Scanner input = new Scanner(System.in);
        System.out.println("请输入英文数字,用逗号分割!");
        String str = input.nextLine();
        String[] inputStr = str.split(",");
        try {
            showNumber(maps, inputStr);
        } catch (InputException e) {
            System.out.println(e.getExcepMessage());
        }
    }

    private static void showNumber(Map<String, Integer> maps, String[] inputStr) throws InputException {
        int count = 0;
        for (int i = 0; i < inputStr.length; i++) {
            inputStr[i] = inputStr[i].toLowerCase();
            if (maps.get(inputStr[i]) != null) {
                count++;
            }
        }
        if (inputStr.length != count) {
            throw new InputException("输入异常！");
        }
        for (int i = 0; i < inputStr.length; i++) {
            System.out.print(maps.get(inputStr[i]));
        }
    }
}

class InputException extends Exception {
    private String message;
    public InputException(String message) {
        this.message = message;
    }
    public String getExcepMessage() {
        return message;
    }
}

文件操作一

import java.io.File;
import java.io.IOException;
import java.nio.file.Files;
import java.nio.file.Paths;
import java.nio.file.attribute.BasicFileAttributes;
import java.nio.file.attribute.FileTime;
import java.text.DateFormat;
import java.text.SimpleDateFormat;

public class CreteDirDemo {
    public static void main(String[] args) throws IOException {
        String path = "C:\\MyDir\\";
        //在mac系统中改为"/Users/用户名/MyDir/"
        File file = new File(path);
        if (!file.exists()) {
            file.mkdir();
        } else {
            System.out.println("创建目录失败！！！目录已存在");
        }
        String fileName = path + "test.txt";
        file = new File(fileName);
        if (file.createNewFile()) {
            System.out.println("创建文件成功");
            BasicFileAttributes bfa  = Files.readAttributes(Paths.get(fileName), BasicFileAttributes.class);
            FileTime date = bfa.creationTime();
            DateFormat df = new SimpleDateFormat("yyyy年MM月dd日");
            String dateCreated = df.format(date.toMillis());
            System.out.println("创建时间:" + dateCreated);
            System.out.println("文件大小:" + bfa.size());
        }
        file.delete();
    }
}

文件操作二

import java.io.File;
public class TraverseDirDemo {
    public static void main(String[] args) {
        String path = "C:\\windows";
        //mac系统为"/Users/"
        File file = new File(path);
        allfile(file);
    }

    public static void allfile(File file) {
        File[] files = file.listFiles();
        if(files!=null && files.length>0) {
            for(File temp:files) {
                //如果文件是一个目录时则递归
                if(temp.isDirectory()) {
                    allfile(temp);
                }else {
                    System.out.println(temp);
                }
            }
        }
    }
}