JAVA 基础学习记录

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JAVA 基础学习记录

Java 基础

1 显示时间(DisplayTime)

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import java.util.Scanner;



public class DisplayTime {



    public static void main(String[] args) {

            try (Scanner in = new Scanner(System.in)) {

                int seconds = in.nextInt();

                int hour = seconds/3600;

                int leftSeconds = seconds - 3600*hour;

                int min = leftSeconds/60;

                int sec = leftSeconds%60;

                System.out.printf("%02d:%02d:%02d",hour,min,sec);

            }

    }

}

//hour*100/100+":"+min*100/100+":"+sec*100/100



2 华氏温度转摄氏温度(FahrenheitToCelsius)

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import java.util.Scanner;



public class FahrenheitToCelsius {



    public static void main(String[] args) {

        try (// TODO Auto-generated method stub

            Scanner input = new Scanner(System.in)) {

            System.out.printf("请输入华氏温度\n");

            double fahrenheit = input.nextDouble();

            double celsius = (fahrenheit - 32)*(5.0/9);

            System.out.printf("摄氏温度为:%.2f\n",celsius);

        }

    }



}

3 分段计算水费(Water)

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import java.util.Scanner;



public class Water {



    public static void main(String[] args) {

        try (// TODO Auto-generated method stub

        Scanner inpute = new Scanner(System.in)) {

            System.out.println("请输入x的值：");

            double x = inpute.nextDouble();

            if(x <= 15) {

                System.out.printf("%.2f\n",4.0*x/3);

            }else {

                System.out.printf("%.2f\n",2.5*x-10.5);

            }

        }



    }



}

4 冒泡排序(BubbleSort)

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package homework;



import java.util.Scanner;



public class BubbleSort {



    public static void main(String[] args) {

        int []a = new int [10];

        System.out.println("请输入10个无序数");

        try (Scanner input = new Scanner (System.in)) {

            for(int i=0;i<a.length;i++) {

                int value = input.nextInt();

                a[i] = value;

            }

        }

        for(int i=0;i<a.length;i++) {

            for(int j=i+1;j<a.length;j++) {

                if(a[i]>a[j]) {

                    int temp = a[i];

                    a[i]=a[j];

                    a[j]=temp;

                }

            }

        }

        for(int i=0;i<a.length;i++) {

            System.out.printf(a[i] + " ");

        }

    }

}

5 求两个数的最大公约数(CommonDivisor)

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package homework;



import java.util.Scanner;



public class CommonDivisor {



    public static void main(String[] args) {

        System.out.println("请输入两个数：");

        try (Scanner input = new Scanner (System.in)) {

            int n1=input.nextInt();

            int n2=input.nextInt();

            System.out.println(commondivisor(n1,n2));

        }

    }

    public static int commondivisor(int n1,int n2) {

        int temp=0;

        for(int i=1;i<=n1 && i<=n2;i++) {

            if(n1%i == 0 && n2%i ==0) {

                temp=i;

            }

        }

        return temp;

    }

}

6 生成 0~99 随机数(RandomDemo)

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package homework;

import java.util.Random;

public class RandomDemo {



    public static void main(String[] args) {

         Random r = new Random();

         int number = r.nextInt(100);

         System.out.println(number);

    }



}

7 判断回文串(CheckPalindrome)

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package homework;



import java.util.Scanner;



public class CheckPalindrome {



    public static void main(String[] args) {

        System.out.println("请输入一个字符串:");

        try (Scanner input = new Scanner(System.in)) {

            String s0 = input.next();

            if(s0.length() % 2 == 0) {

                StringBuilder s1 = new StringBuilder(s0.substring(0, s0.length()/2));

                StringBuilder s2 = new StringBuilder(s0.substring(s0.length()/2, s0.length()));

                s2.reverse();

                if(String.valueOf(s1).equals(String.valueOf(s2))) {

                    System.out.println("这是一个回文串");

                }else {

                    System.out.println("这不是一个回文串");

                }

            }else {

                StringBuilder s1 = new StringBuilder(s0.substring(0, s0.length()/2));

                StringBuilder s2 = new StringBuilder(s0.substring(s0.length()/2 + 1, s0.length()));

                s2.reverse();

                if(String.valueOf(s1).equals(String.valueOf(s2))) {

                    System.out.println("这是一个回文串");

                }else {

                    System.out.println("这不是一个回文串");

                }

            }

        }

    }

}

8 记事本(NoteBook)

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package notebook;



import java.util.ArrayList;



public class NoteBook {



    private ArrayList<String> notes = new ArrayList<String>();

    public void add(String s) {

        notes.add(s);

    }



    public int getSize() {

        return notes.size();

    }



    public String getNote(int index) {

        return notes.get(index);

    }



    public void removeNote(int index) {

        notes.remove(index);

    }



    public String[] list() {

        String[] a = new String[notes.size()];

        notes.toArray(a);

        return a;

    }



    public static void main(String[] args) {

        NoteBook notebook = new NoteBook();

        notebook.add("NO.1");

        System.out.println(notebook.getNote(0));

        notebook.add("No.2");

        System.out.println(notebook.getNote(1));

        notebook.removeNote(1);

        System.out.println(notebook.getSize());

        String[] a = notebook.list();

        for(int i=0; i<notebook.getSize(); i++) {

            System.out.println(a[i]);

        }

    }

}