面试题：

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自动装箱:把基本数据类型会自动的变成其对应的包装类
自动拆箱:把包装类自动的变成其对象的基本数据类型

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package Integer;

public class Demo {
    public static void main(String[] args) {
        Integer i = 10;
        String binaryString = Integer.toBinaryString(i);
        String hexString = Integer.toHexString(i);
        String octalString = Integer.toOctalString(i);
        System.out.println("二进制:" + binaryString + "\n十六进制:" + hexString + "\n八进制:" + octalString);

        //4.将字符串类型的整数转成int类型的整数
        //强类型语言:每种数据在java中都有各自的数据类型
        //在计算的时候，如果不是同一种数据类型，是无法直接计算的。

        //字符串已经转换成整数类型
        int i1 = Integer.parseInt(binaryString);
        System.out.println(i1);
        //验证是否转换成功
        System.out.println(i1 + 1);

        //细节1:
        //在类型转换的时候，括号中的参数只能是数字不能是其他，否则代码会报错
        //细节2:
        //8种包装类当中，除了character都有对应的parsexxx的方法，进行类型转换
        String str ="true";
        boolean b=Boolean.parseBoolean(str);
        System.out.println(b);
    }
}

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package Integer;

import java.util.Scanner;

public class Demo1 {
    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        System.out.println("请输入：");
        String s = sc.nextLine();

        //进行类型转换
        int i = Integer.parseInt(s);
        System.out.println(i);
        //验证
        System.out.println(i+1);
    }
}

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package execrise;

import javax.sound.sampled.SourceDataLine;
import java.util.ArrayList;
import java.util.Scanner;

public class Demo2 {
    public static void main(String[] args) {
        ArrayList<Integer> list = new ArrayList<>();
        Scanner sc = new Scanner(System.in);
        int sum = 0;
        while (sum <= 200) {
            System.out.println("请输入整数:");
            String num1 = sc.nextLine();
            int num = Integer.parseInt(num1);
            if (num >= 1 && num <= 100) {
                list.add(num);
                sum += num;
            } else {
                System.out.print("输入有误,");
            }
        }
        System.out.print("集合中的数据为：");
        for (int i = 0; i < list.size(); i++) {
            System.out.print(list.get(i) + " ");
        }
    }
}

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方法1：

package execrise;

import java.util.Scanner;

public class Demo3 {
    public static void main(String[] args) {
        Scanner scanner = new Scanner(System.in);
        String s;
        while (true) {
            System.out.println("请输入字符串");
            s = scanner.nextLine();
            if (judement(s)) {
                break;
            } else {
                System.out.print("输入错误,");
            }
        }
        char[] array = s.toCharArray();
        int number = 0;
        for (int i = 0; i < array.length; i++) {
            int i1 = array[i] - '0';
            number = number * 10 + i1;
        }
        System.out.println("字符串转换后的数字为:" + number);
        //验证
        System.out.println(number + 1);

    }

    public static boolean judement(String string) {
        char[] array = string.toCharArray();
        for (int i = 0; i < array.length; i++) {
            if (array[i] < '0' || array[i] > '9') {
                return false;
            }
        }

        if (string.length() < 1 || string.length() > 10) {
            return false;
        }

        if (string.startsWith("0")) {
            return false;
        }

        return true;
    }
}

方法2：

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package execrise;

import java.util.Scanner;

public class Demo4 {
    public static void main(String[] args) {
        Scanner scanner = new Scanner(System.in);
        System.out.println("请输入十进制整数:");
        String s = scanner.nextLine();
        int number = Integer.parseInt(s);
        toBinary(number);
    }

    private static void toBinary(int number) {
        String s = "";
        while (number != 0) {
            int yu = number % 2;
            number = number / 2;
            s = yu + s;
        }
        System.out.println("十进制对应二进制为:" + s);
    }
}

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JDK7:

package execrise;

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

public class Demo5 {
    public static void main(String[] args) throws ParseException {
        Date date = new Date();
        //System.out.println(System.currentTimeMillis());

        String s = "2000-1-1";
        SimpleDateFormat simpleDateFormat = new SimpleDateFormat("yyyy-MM-dd");
        Date parse = simpleDateFormat.parse(s);
        long l = date.getTime() - parse.getTime();

        System.out.println(l / 1000 / 60 / 60 / 24);
    }
}

JDK8

package execrise;

import java.time.LocalDateTime;
import java.time.temporal.ChronoUnit;

public class Demo6 {
    public static void main(String[] args) {
        LocalDateTime now = LocalDateTime.now();
        LocalDateTime localDateTime = LocalDateTime.of(1999, 2, 12, 4, 0, 0);
        System.out.println(ChronoUnit.DAYS.between(localDateTime, now));
    }
}

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JDK7:

方法1：

package execrise;

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

public class Demo7 {
    public static void main(String[] args) throws ParseException {
        String string1 = "2024-1-1";
        String string2 = "2025-1-1";
        SimpleDateFormat sdf = new SimpleDateFormat("yyyy-MM-dd");
        Date parse1 = sdf.parse(string1);
        Date parse2 = sdf.parse(string2);
        long l = parse2.getTime() - parse1.getTime();
        if (l / (1000 * 60 * 60 * 24) == 365) {
            System.out.println("不是闰年");
        } else {
            System.out.println("是闰年");
        }

    }
}

方法2：

JDK8：

方法1：

package execrise;

import java.time.LocalDateTime;
import java.time.temporal.ChronoUnit;

public class Demo8 {
    public static void main(String[] args) {
        LocalDateTime localDateTime = LocalDateTime.of(2025, 1, 1, 0, 0);
        LocalDateTime localDateTime1 = LocalDateTime.of(2024, 1, 1, 0, 0);
        if (ChronoUnit.DAYS.between(localDateTime1, localDateTime) == 365) {
            System.out.println("不是闰年");
        } else {
            System.out.println("是闰年");
        }
    }
}

方法2：