牛客网语法篇之Java入门

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2022-11-26


JAVA1 类型转换

import java.util.Scanner;

public class Main {
    public static void main(String[] args) {
        Scanner scanner = new Scanner(System.in);
        double d = scanner.nextDouble();
        System.out.println(Main.typeConversion(d));
    }
    public static int typeConversion(double d){

        //write your code here......
        return (int)d;

    }
}

JAVA2 简单运算

import java.util.Scanner;

public class Main {
    public static void main(String[] args) {
        Scanner scanner = new Scanner(System.in);
        int a = scanner.nextInt();
        int b = scanner.nextInt();
        scanner.close();

        //write your code here......
        int sum = a + b;
        int difference = a > b ? a - b : b - a;
        int product = a * b;
        int quotient = a > b ? a / b : b / a;
        int module = a > b ? a % b : b % a;
        System.out.println(sum + " " + difference + " " + product + " " + quotient + " " + module);

    }
}

JAVA3 四舍五入

import java.util.Scanner;

public class Main {
    public static void main(String[] args) {
        Scanner scanner = new Scanner(System.in);
        double d= scanner.nextDouble();

        //write your code here......
        int i = (int)(d * 10) % 10 >= 5 ? (int)d + 1 : (int)d;

        System.out.println(i);
    }
}

JAVA4 交换变量值

import java.util.Scanner;

public class Main {
    public static void main(String[] args) {
        Scanner scanner = new Scanner(System.in);
        int a = scanner.nextInt();
        int b = scanner.nextInt();

        //write your code here.......
        int temp = a;
        a = b;
        b = temp;
        

        System.out.println(a+" "+b);
    }
}

JAVA5 计算商场折扣

import java.util.*;

public class Main {
    public static void main(String[] args) {
        Scanner console = new Scanner(System.in);
        int price = console.nextInt();
        int cost = 0;

        //write your code here......
        if (price < 100) {
            cost = price;
        } else if (price < 500) {
            cost = (int)(price * 0.9);
        } else if (price < 2000) {
            cost = (int)(price * 0.8);
        } else if (price < 5000) {
            cost = (int)(price * 0.7);
        } else {
            cost = (int)(price * 0.6);
        }

        System.out.println(cost);
    }
}

JAVA6 判断体重指数

import java.util.Scanner;

public class Main {
    public static void main(String[] args) {
        Scanner scanner = new Scanner(System.in);
        double height = scanner.nextDouble();
        double weight = scanner.nextDouble();

        //write your code here......
        double bmi = weight / (height * height);
        if (bmi < 18.5) {
            System.out.println("偏瘦");
        } else if (bmi < 20.9) {
            System.out.println("苗条");
        } else if (bmi < 24.9) {
            System.out.println("适中");
        } else {
            System.out.println("偏胖");
        }

    }
}

JAVA7 判断学生成绩等级

import java.util.Scanner;

public class Main {
    public static void main(String[] args) {
        Scanner scanner = new Scanner(System.in);
        String grade =scanner.next();

        //write your code here......
        switch (grade) {
            case "A":
                System.out.println("优秀");
                break;
            case "B":
                System.out.println("良好");
                break;
            case "C":
                System.out.println("及格");
                break;
            case "D":
                System.out.println("不及格");
                break;
            default:
                System.out.println("未知等级");
        }

    }
}

JAVA8 邮箱验证

import java.util.Scanner;

public class Main {
    public static void main(String[] args) {

        Scanner scanner = new Scanner(System.in);
        String str = scanner.next();
        String emailMatcher="[a-zA-Z0-9]+@[a-zA-Z0-9]+\\.[a-zA-Z0-9]+";

        //write your code here......
        if (str.matches(emailMatcher)) {
            System.out.println("邮箱格式合法");
        } else {
            System.out.println("邮箱格式不合法");
        }

    }
}

JAVA9 数列求和

public class Main {
    public static void main(String[] args) {

        //write your code here........
        long sum = 0;
        for (long i = 9; i <= 9999999999L; i = i * 10 + 9) {
            sum += i;
        }
        System.out.println(sum);

    }
}

JAVA10 统计输入正数个数

import java.util.*;

public class Main {
    public static void main(String[] args) {
        int count = 0;
        Scanner scanner = new Scanner(System.in);

        //write your code here......
        while (scanner.nextInt() > 0) {
            count++;
        }
        System.out.println(count);

    }
}

JAVA11 求最小公倍数

import java.util.*;

public class Main {
    public static void main(String[] args) {
        Scanner console = new Scanner(System.in);
        int m = console.nextInt();
        int n = console.nextInt();
        int result = getCM(m, n);
        System.out.println(result);
    }

    public static int getCM(int m, int n){

        //write your code here......
        int a = m > n ? m : n;
        int b = m > n ? n : m;
        
        while (b > 0) {
            int temp = a % b;
            a = b;
            b = temp;
        }
        
        return m * n / a;

    }
}

JAVA12 小球走过路程计算

import java.util.Scanner;

public class Main {
    public static void main(String[] args) {
        Scanner scanner=new Scanner(System.in);
        float h=scanner.nextFloat();
        int n =scanner.nextInt();

        //write your code here......
        float sum = h;
        h /= 2;
        for (int i = 1; i < n; ++i) {
            sum += h * 2;
            h /= 2;
        }
        System.out.println(String.format("%.3f", h)+" "+String.format("%.3f", sum));

        //输出格式为：System.out.println(String.format("%.3f", h)+" "+String.format("%.3f", sum));
        

    }
}

JAVA13 求平均数

import java.util.Scanner;

public class Main {

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

        //write your code here......
        int number;
        double avg = 0;
        int count = 0;
        while ((number = scan.nextInt()) != -1) {
            avg += number;
            count++;
        }
        avg /= count;

        //输出格式为：System.out.println(String.format("%.2f",avg));
        System.out.println(String.format("%.2f",avg));

    }
}

JAVA14 判断质数

import java.util.Scanner;

public class Main {
    public static void main(String[] args) {
        Main main = new Main();
        Scanner scan = new Scanner(System.in);
        int number = scan.nextInt();
        System.out.println(main.isPrimeNumber(number));
    }

    public Boolean isPrimeNumber(int number) {

        //write your code here......
        for (int i = 2; i * i <= number; i++) {
            if (number % i == 0) {
                return false;
            }
        }
        return true;

    }
}

JAVA15 计算整数位数

import java.util.Scanner;

public class Main {
    public static void main(String[] args) {
        Scanner scan = new Scanner(System.in);
        int num = scan.nextInt();
        scan.close();

        //write code here......
        if (num > 0) {
            int numOfDigits = 0;
            while (num > 0) {
                numOfDigits++;
                num /= 10;
            }
            System.out.println(numOfDigits);
        } else {
            System.out.println(num);
        }

    }
}

JAVA16 数组遍历

import java.util.Scanner;

public class Main {
    public static void main(String[] args) {
        int[] ary = new int[6];
        int max;
        int min;
        Scanner scanner = new Scanner(System.in);
        for (int i = 0; i <ary.length ; i++) {
            ary[i]=scanner.nextInt();
        }

        //write your code here......
        max = ary[0];
        min = ary[0];
        for (int i = 1; i < ary.length; i++) {
            max = max < ary[i] ? ary[i] : max;
            min = min > ary[i] ? ary[i] : min;
        }

        System.out.println(max+" "+min);
    }
}

JAVA17 数组倒转

import java.util.Arrays;
import java.util.Scanner;

public class Main {
    public static void main(String[] args) {
        int[] arr = new int[6];
        Scanner scanner = new Scanner(System.in);
        for (int i = 0; i < arr.length; i++) {
            arr[i] = scanner.nextInt();
        }
        System.out.println(Arrays.toString(arr));

        //write your code here......
        for (int i = 0, j = arr.length - 1; i < j; i++, j--) {
            int temp = arr[i];
            arr[i] = arr[j];
            arr[j] = temp;
        }
        

        System.out.println(Arrays.toString(arr));
    }
}

JAVA18 二维数组求和

public class Main {
    public static void main(String[] args) {
        int[][]  arr = {{11,33,55},{22,44,66,88},{131,214,315,146},{928,827,726,625},{424,525}};
        int sum=add(arr);
        System.out.println(sum);
    }

    public static int add(int[][] arr) {
        int sum=0;

        //write your code here......
        for (int i = 0; i < arr.length; i++) {
            for (int j = 0; j < arr[i].length; j++) {
                sum += arr[i][j];
            }
        }

        return sum;
    }
}

JAVA19 修改Data类的定义

import java.util.Scanner;

public class Main {

    public static void main(String[] args) {
        Scanner scanner = new Scanner(System.in);
        while (scanner.hasNextInt()) {
            int x = scanner.nextInt();
            int y = scanner.nextInt();
            Data data = new Data(x, y);
            System.out.println(data.getX() + data.getY());
        }
    }

}

class Data {

    private int x;
    private int y;

    Data(int x, int y) {
        this.x = x;
        this.y = y;
    }

    public int getX() {
        return x;
    }

    public int getY() {
        return y;
    }

}

JAVA20 验证年龄

import java.util.Scanner;

public class Main {

    public static void main(String[] args) {
        Person p = new Person();
        Scanner scanner = new Scanner(System.in);
        while (scanner.hasNextInt()) {
            int age = scanner.nextInt();
            p.setAge(age);
            System.out.println(p.getAge());
        }
    }

}

class Person {

    private int age;

    //write your code here......
    public void setAge(int age) {
        this.age = age;
    }
    
    public int getAge() {
        if (age < 0) {
            return 0;
        } else if (age > 200) {
            return 200;
        } else {
            return age;
        }
    }

}

JAVA21 补全构造方法

import java.util.Scanner;

public class Main {

    public static void main(String[] args) {
        Scanner scanner = new Scanner(System.in);
        while (scanner.hasNextInt()) {
            int x = scanner.nextInt();
            int y = scanner.nextInt();
            int z = scanner.nextInt();
            Sub sub = new Sub(x, y, z);
            System.out.println(sub.calculate());
        }
    }

}

class Base {

    private int x;
    private int y;

    public Base(int x, int y) {
        this.x = x;
        this.y = y;
    }

    public int getX() {
        return x;
    }

    public int getY() {
        return y;
    }

}

class Sub extends Base {

    private int z;

    public Sub(int x, int y, int z) {

        //write your code here
        super(x, y);
        this.z = z;

    }

    public int getZ() {
        return z;
    }

    public int calculate() {
        return super.getX() * super.getY() * this.getZ();
    }

}

JAVA22 重写计算逻辑

import java.util.Scanner;

public class Main {

    public static void main(String[] args) {
        Scanner scanner = new Scanner(System.in);
        while (scanner.hasNextInt()) {
            int x = scanner.nextInt();
            int y = scanner.nextInt();
            Sub sub = new Sub(x, y);
            sub.calculate();
        }
    }

}

class Base {

    private int x;
    private int y;

    public Base(int x, int y) {
        this.x = x;
        this.y = y;
    }

    public int getX() {
        return x;
    }

    public int getY() {
        return y;
    }

    public void calculate() {
        System.out.println(getX() * getY());
    }

}

class Sub extends Base {

    //write your code here......
    public Sub(int x, int y) {
        super(x, y);
    }
    
    public void calculate() {
        System.out.println(getY() == 0 ? "Error" : getX() / getY());
    }

}

JAVA23 定义打印方法

import java.util.Scanner;

public class Main {

    public static void main(String[] args) throws Exception {
        Scanner scanner = new Scanner(System.in);
        while (scanner.hasNext()) {
            String className = scanner.next();
            // print就是需要你定义的方法
            print(Class.forName(className).newInstance());
        }
    }

    //write your code here......
    private static void print(Object clazz) {
        System.out.println(clazz.toString());
    }

}

class First {
    public String toString() {
        return "First";
    }
}

class Second {
    public String toString() {
        return "Second";
    }
}

class Third {
    public String toString() {
        return "Third";
    }
}

JAVA24 类型判断

import java.util.Scanner;

public class Main {

    public static void main(String[] args) throws Exception {
        Scanner scanner = new Scanner(System.in);
        while (scanner.hasNext()) {
            String className = scanner.next();
            Base obj = (Base) Class.forName(className).newInstance();
            System.out.println(getClassName(obj));
        }
    }

    public static String getClassName(Base obj) {

        //write your code here......
        return obj.getClass().getName();

    }

}

class Base {

}

class Sub1 extends Base {

}

class Sub2 extends Base {

}

JAVA25 实现抽象方法

import java.util.Scanner;

public class Main {

    public static void main(String[] args) {
        // Sub是需要你定义的子类
        Base base = new Sub();

        Scanner scanner = new Scanner(System.in);
        while (scanner.hasNextInt()) {
            int x = scanner.nextInt();
            int y = scanner.nextInt();
            base.setX(x);
            base.setY(y);
            System.out.println(base.calculate());
        }
    }

}

abstract class Base {

    private int x;
    private int y;

    public int getX() {
        return x;
    }

    public void setX(int x) {
        this.x = x;
    }

    public int getY() {
        return y;
    }

    public void setY(int y) {
        this.y = y;
    }

    public int calculate() {
        if (avg() == 0) {
            return 0;
        } else {
            return sum() / avg();
        }
    }

    /**
     * 返回x和y的和
     */
    public abstract int sum();

    /**
     * 返回x和y的平均值
     */
    public abstract int avg();

}

class Sub extends Base {

    //write your code here......
    public int sum() {
        return getX() + getY();
    }
    
    public int avg() {
        return (getX() + getY()) / 2;
    }

}

JAVA26 实现接口

import java.util.Scanner;

public class Main {

    public static void main(String[] args) {
        Comparator comparator = new ComparatorImpl();

        Scanner scanner = new Scanner(System.in);
        while (scanner.hasNextInt()) {
            int x = scanner.nextInt();
            int y = scanner.nextInt();
            System.out.println(comparator.max(x, y));
        }
    }

}

interface Comparator {
    /**
     * 返回两个整数中的最大值
     */
    int max(int x, int y);
}

//write your code here......
class ComparatorImpl implements Comparator {
    public int max(int x, int y) {
        return x > y ? x : y;
    }
}

JAVA27 重写父类方法

import java.util.Scanner;

public class Main {

    public static void main(String[] args) {
        Scanner scanner = new Scanner(System.in);
        while (scanner.hasNextInt()) {
            int x = scanner.nextInt();
            int y = scanner.nextInt();
            Sub sub = new Sub(x, y);
            System.out.println(sub.sum());
        }
    }

}

class Base {

    private int x;
    private int y;

    public Base(int x, int y) {
        this.x = x;
        this.y = y;
    }

    public int getX() {
        return x;
    }

    public final int getY() {
        return y;
    }

    public final int sum() {
        return getX() + getY();
    }

}

class Sub extends Base {

    public Sub(int x, int y) {
        super(x, y);
    }

    //write your code here......
    public int getX() {
        return 10 * super.getX();
    }
}

JAVA28 创建单例对象

public class Main {

    public static void main(String[] args) {
        Singleton s1 = Singleton.getInstance();
        Singleton s2 = Singleton.getInstance();
        System.out.println(s1 == s2);
    }

}

class Singleton {

    private static Singleton instance;

    private Singleton() {

    }

    //write your code here......
    public static Singleton getInstance() {
        return instance;
    }

}

JAVA29 动态字符串

import java.util.Scanner;

public class Main {
    public static void main(String[] args) {
        Scanner scanner = new Scanner(System.in);
        String str = scanner.next();

        //write your code here......
        StringBuilder modifiedStr = new StringBuilder();
        int ptr = str.length();
        modifiedStr.append(str, Math.max(ptr - 3, 0), ptr);
        ptr -= 3;
        while (ptr > 0) {
            modifiedStr.insert(0, str.substring(Math.max(ptr - 3, 0), ptr) + ",");
            ptr -= 3;
        }

        System.out.println(modifiedStr.toString());

    }
}

JAVA30 统计字符串中字母出现次数

import java.util.Scanner;

public class Main {
    public static void main(String[] args) {
        String string = "H e l l o ! n o w c o d e r";
        Scanner scanner= new Scanner(System.in);
        String word = scanner.next();
        scanner.close();
        System.out.println(check(string, word));
    }

    public static int check(String str, String word) {

        //write your code here......
        char query = word.charAt(0);
        int count = 0;
        for (int i = 0; i < str.length(); i++) {
            if (str.charAt(i) == query) {
                count++;
            }
        }
        return count;

    }
}

JAVA31 十进制数转二进制数

import java.util.*;

public class Main {
    public static void main(String[] args) {
        Scanner scanner = new Scanner(System.in);
        int num = scanner.nextInt();

        //write your code here......
        System.out.println(Integer.toBinaryString(num));

    }
}

JAVA33 掷骰子游戏

import java.util.Random;
import java.util.Scanner;

public class Main {

    public static void main(String[] args) {
        Scanner scanner = new Scanner(System.in);
        while (scanner.hasNextInt()) {
            int seed = scanner.nextInt();
            Random random = new Random(seed);

            //write your code here......
            System.out.println(random.nextInt(6) + 1);

        }
    }

}

JAVA34 求绝对值，平方根，对数，正弦值

import java.util.Scanner;

public class Main {
    public static void main(String[] args) {
        Scanner scanner=new Scanner(System.in);
        double num = scanner.nextDouble();

        //write your code here......
        System.out.println(Math.abs(num));
        System.out.println(Math.sqrt(num));
        System.out.println(Math.log(num));
        System.out.println(Math.sin(num));

    }
}

JAVA35 输出某一年的各个月份的天数

import java.util.Calendar;
import java.util.Scanner;

public class Main {
    public static void main(String[] args) {
        Scanner console = new Scanner(System.in);
        int year = console.nextInt();

        //write your code here......
        Calendar c = Calendar.getInstance();
        for (int month = 1; month <= 12; month++) {
            c.set(year, month - 1, 1);
            System.out.println(year + "年" + month + "月:" + c.getActualMaximum(Calendar.DAY_OF_MONTH) + "天");
        }

    }
}

JAVA36 日期换算

import java.text.ParseException;
import java.text.SimpleDateFormat;
import java.util.Date;
import java.util.Scanner;

public class Main {
    public static void main(String[] args) throws ParseException {
        SimpleDateFormat sdf = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss");
        Scanner in = new Scanner(System.in);
        String str1 = in.nextLine();

        //write your code here......
        try {
            Date date = new SimpleDateFormat("yyyy MM dd HH mm ss").parse(str1);
            System.out.println("北京时间为：" + new SimpleDateFormat("yyyy-MM-dd HH:mm:ss").format(date));
            System.out.println("纽约时间为：" + new SimpleDateFormat("yyyy-MM-dd HH:mm:ss").format(date.getTime() - 12 * 60 * 60 * 1000));
            
        } catch (ParseException ex) {
            System.out.println("您输入的数据不合理");
        }

    }
}

JAVA37 判断学生成绩

import java.util.*;

public class Main {
    public static void main(String[] args) {
        Scanner scanner = new Scanner(System.in);
        int score = scanner.nextInt();

        //write your code here......
        try {
            if (0 <= score && score <= 100) {
                System.out.println(score);
            } else {
                throw new ScoreException("分数不合法");
            }
        } catch (ScoreException ex) {
            System.out.println(ex.getMessage());
        }
    }
}

class ScoreException extends Exception {

    //write your code here......
    public ScoreException() {
        super();
    }
    
    public ScoreException(String message) {
        super(message);
    }

}

JAVA38 字符串去重

import java.util.HashSet;
import java.util.Scanner;

public class Main {
    public static void main(String[] args) {
        Scanner scanner = new Scanner(System.in);
        String str = scanner.nextLine();
        scanner.close();
        HashSet<Character> hs = new HashSet<>();

        //write your code here......
        for (int i = 0; i < str.length(); i++) {
            hs.add(str.charAt(i));
        }

        for (char c:hs) {
            System.out.print(c);
        }
    }
}

JAVA39 集合遍历

import java.util.ArrayList;
import java.util.Iterator;
import java.util.List;
import java.util.Scanner;

public class Main {
    public static void main(String[] args) {
        Scanner scanner = new Scanner(System.in);
        List<Integer> list = new ArrayList<>();
        int num1 = scanner.nextInt();
        int num2 = scanner.nextInt();
        int num3 = scanner.nextInt();
        int num4 = scanner.nextInt();
        int num5 = scanner.nextInt();
        scanner.close();
        list.add(num1);
        list.add(num2);
        list.add(num3);
        list.add(num4);
        list.add(num5);
        System.out.print("普通for循环:");

        //write your code here......
        for (int i = 0; i < list.size(); i++) {
            System.out.print(list.get(i) + " ");
        }
        

        System.out.println();
        System.out.print("增强for循环:");

        //write your code here......
        for (Integer x : list) {
            System.out.print(x + " ");
        }
        

        System.out.println();
        System.out.print("迭代器遍历:");

        //write your code here......
        Iterator iter = list.listIterator();
        while (iter.hasNext()) {
            System.out.print(iter.next() + " ");
        }

        System.out.println();
    }
}

JAVA40 排队系统

import java.util.*;

public class Main {
    public static void main(String[] args) {
        Guest guest1 = new Guest("小明",false);
        Guest guest2 = new Guest("小军",false);
        Guest vipGuest = new Guest("小红",true);
        Deque<Guest> deque = new ArrayDeque<>();
        deque.add(guest1);
        deque.add(guest2);

        //write your code here......
        deque.push(vipGuest);
        

        System.out.println(deque);
    }
}
class Guest{
    String name;
    Boolean vip;

    @Override
    public String toString() {
        return name;
    }

    public Guest(String name, Boolean vip) {
        this.name = name;
        this.vip = vip;

    }
}

JAVA41 Head and Tail of the Queue

import java.util.ArrayDeque;
import java.util.Scanner;

public class Main {

    public static void main(String[] args) {
        ArrayDeque deque = new ArrayDeque();

        Scanner scanner = new Scanner(System.in);
        while (scanner.hasNext()) {
            String name = scanner.next();
            // 初始化队列中的数据
            deque.offerLast(name);
        }

        // write your code here......
        boolean fromFirst = true;
        while (!deque.isEmpty()) {
            if (fromFirst) {
                System.out.println(deque.pollFirst());
            } else {
                System.out.println(deque.pollLast());
            }
            fromFirst = !fromFirst;
        }

    }

}

JAVA42 统计一句话中重复单词的个数

import java.util.*;

public class Main {
    public static void main(String[] args) {
        Scanner scanner = new Scanner(System.in);
        String line = scanner.nextLine();
        Map<Character, Integer> map = new LinkedHashMap<Character, Integer>();

        //write your code here......
        for (int i = 0; i < line.length(); i++) {
            char ch = line.charAt(i);
            if (('A' <= ch && ch <= 'Z') || ('a' <= ch && ch <= 'z')) {
                map.put(ch, map.getOrDefault(ch, 0) + 1);
            }
        }
        

        Set<Map.Entry<Character, Integer>> entrys = map.entrySet();
        for (Map.Entry<Character, Integer> entry : entrys) {
            System.out.println(entry.getKey() + ":" + entry.getValue());
        }
    }
}

JAVA43 map简单应用

import java.util.*;

public class Main {
    public static void main(String[] args) {
        Scanner scanner  = new Scanner(System.in);
        String name = scanner.next();
        Map<Integer, String> map = new HashMap<Integer, String>();
        map.put(1, "Amy");
        map.put(2, "Joe");
        map.put(3, "Tom");
        map.put(4, "Susan");

        //write your code here......
        for (Integer key : map.keySet()) {
            System.out.println(key + ":" + map.get(key));
        }
        map.put(5, name);
        map.remove(4);
        map.replace(3, "Tommy");
        System.out.println();
        for (Integer key : map.keySet()) {
            System.out.println(key + ":" + map.get(key));
        }

    }
}

JAVA44 集合排序

import java.util.ArrayList;
import java.util.Collections;
import java.util.List;
import java.util.Scanner;

public class Main {
    public static void main(String[] args) {
        Scanner scanner = new Scanner(System.in);
        Customer customer1 = new Customer("小明",scanner.nextInt());
        Customer customer2 = new Customer("小军",scanner.nextInt());
        Customer customer3 = new Customer("小红",scanner.nextInt());
        List<Customer> customers = new ArrayList<>();
        customers.add(customer1);
        customers.add(customer2);
        customers.add(customer3);

        //write your code here......
        Collections.sort(customers);

        System.out.println(customers);

    }
}

class Customer implements Comparable<Customer>{
    private String name;
    private int consumption;

    public Customer(String name, int consumption) {
        this.name = name;
        this.consumption = consumption;
    }

    @Override
    public String toString() {
        return "Customer{" +
                "name='" + name + '\'' +
                ", consumption=" + consumption +
                '}';
    }

    //write your code here......
    public int getConsumption() {
        return consumption;
    }
    
    public int compareTo(Customer customer) {
        return customer.getConsumption() - this.consumption;
    }

}

JAVA45 判断各类型字符个数

import java.util.Scanner;

public class Main {
    public static void main(String[] args) {
        int numbers = 0;
        int words = 0;
        int space = 0;
        int other = 0;
        Scanner scanner = new Scanner(System.in);
        String str = scanner.nextLine();

        //write your code here......
        for (int i = 0; i < str.length(); i++) {
            char ch = str.charAt(i);
            if (('a' <= ch && ch <= 'z') || ('A' <= ch && ch <= 'Z')) {
                words++;
            } else if ('0' <= ch && ch <= '9') {
                numbers++;
            } else if (ch == ' ') {
                space++;
            } else {
                other++;
            }
        }

        System.out.println("英文字母"+words+"数字"+numbers+"空格"+space+"其他"+other);
    }
}

JAVA46 编写个人所得税计算程序

import java.util.*;

public class Main {
    public static void main(String[] args) {
        List<Employee> employees = new ArrayList<>();

        //write your code here......
        employees.add(new Employee("小明", 2500));
        employees.add(new Employee("小军", 8000));
        employees.add(new Employee("小红", 100000));
        
        for (Employee employee : employees) {
            double salaryForTax = employee.getSalary() - 3500;
            double tax = 0;
            if (salaryForTax <= 0) {
                tax = 0;
            } else if (salaryForTax <= 1500) {
                tax = salaryForTax * 0.03;
            } else if (salaryForTax <= 4500) {
                tax = salaryForTax * 0.10 - 105;
            } else if (salaryForTax <= 9000) {
                tax = salaryForTax * 0.20 - 555;
            } else if (salaryForTax <= 35000) {
                tax = salaryForTax * 0.25 - 1005;
            } else if (salaryForTax <= 55000) {
                tax = salaryForTax * 0.30 - 2755;
            } else if (salaryForTax <= 80000) {
                tax = salaryForTax * 0.35 - 5505;
            } else {
                tax = salaryForTax * 0.45 - 13505;
            }
            System.out.println(employee.getName() + "应该缴纳的个人所得税是：" + String.format("%.1f", tax));
        }

    }
}
class Employee{
    private String name;
    private double salary;
    public Employee(String name, double salary) {
        this.name = name;
        this.salary = salary;
    }
    public String getName() {
        return name;
    }

    public double getSalary() {
        return salary;
    }
}

JAVA47 记录点赞用户

import java.util.*;

public class Main {

    public static void main(String[] args) {
        LikeRecorder recorder = new LikeRecorderImpl();

        Scanner scanner = new Scanner(System.in);
        while (scanner.hasNext()) {
            String name = scanner.next();
            recorder.like(name);
        }

        System.out.println(Arrays.toString(recorder.getLikeUsers()));
    }

}

/**
 * 点赞记录器
 */
interface LikeRecorder {

    /**
     * 若用户没有点赞过，则记录此次点赞行为。
     * 若用户曾经点赞过，则删除用户点赞记录。
     *
     * @param username 用户名
     */
    void like(String username);

    /**
     * 返回所有点赞的用户名
     *
     * @return 用户名数组
     */
    String[] getLikeUsers();

}

class LikeRecorderImpl implements LikeRecorder {

    // write your code here......
    private HashSet<String> users = new HashSet<>();
    
    public void like(String username) {
        if (users.contains(username)) {
            users.remove(username);
        } else {
            users.add(username);
        }
    }
    
    public String[] getLikeUsers() {
        return users.toArray(new String[users.size()]);
    }

}

JAVA48 回文数判断

import java.util.Scanner;

public class Main {
    public static void main(String[] args) {
        Scanner console = new Scanner(System.in);
        Main main = new Main();
        int number = console.nextInt();
        System.out.println(main.palindromeNumber(number));
    }

    public Boolean palindromeNumber(int number) {

        //write your code here......
        StringBuffer numStr = new StringBuffer("" + number);
        return numStr.toString().equals(numStr.reverse().toString());

    }
}

JAVA49 判断素数个数

import java.util.Scanner;

public class Main {
    public static void main(String[] args) {
        Scanner scanner = new Scanner(System.in);
        int start = scanner.nextInt();
        int end = scanner.nextInt();
        method(start,end);
    }

    public static void method(int start, int end) {
        int count=0;

        //write your code here......
        if (start > end) {
            int temp = start;
            start = end;
            end = temp;
        }
        
        for (int i = start <= 2 ? 3 : start; i <= end; ++i) {
            boolean isPrime = true;
            for (int j = 2; j * j <= i; j++) {
                if (i % j == 0) {
                    isPrime = false;
                    break;
                }
            }
            count += isPrime ? 1 : 0;
        }
        

        System.out.println(start+"到"+end+"之间有"+count+"个大于2的素数");
    }
}

JAVA50 根据周长求面积

import java.util.Scanner;

public class Main {

    public static void main(String[] args) {
        Scanner scanner = new Scanner(System.in);
        while (scanner.hasNextDouble()) {
            double s = scanner.nextDouble();
            // Circle和Square是需要你定义的类
            System.out.println(String.format("%.3f",new Circle(s).getArea()));
            System.out.println(String.format("%.3f", new Square(s).getArea()));
        }
    }

}

class Shape {

    private double s; // 周长

    public Shape(double s) {
        this.s = s;
    }

    public double getS() {
        return s;
    }

}

interface Area {
    double getArea(); // 面积
}

// 圆形
class Circle extends Shape implements Area {

    //write your code here......
    public Circle(double s) {
        super(s);
    }
    
    public double getArea() {
        return getS() * getS() / (4 * Math.PI);
    }

}

// 方形
class Square extends Shape implements Area {

    //write your code here......
    public Square(double s) {
        super(s);
    }
    
    public double getArea() {
        return getS() * getS() / 16;
    }

}

JAVA51 冒泡排序

import java.util.Arrays;
import java.util.Scanner;
public class Main {
    public static void main(String[] args) {
        Scanner scanner = new Scanner(System.in);
         int[] arr = new int[7];
        for (int i = 0; i < arr.length; i++) {
            arr[i] = scanner.nextInt();
        }
        scanner.close();

        //write your code here......
        for (int j = arr.length - 1; j > 0; j--) {
            for (int i = j - 1; i >= 0; i--) {
                if (arr[i] > arr[j]) {
                    int temp = arr[i];
                    arr[i] = arr[j];
                    arr[j] = temp;
                }
            }
        }
        

        for (int k = 0; k < arr.length; k++) {
            System.out.print(arr[k]+" ");
        }
    }
}

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