大数据学习第四天

一.作业纠错

　　1.从控制台输入两个英文字母，输出这两个英文字母之间的所有字母（包含大小写）

package day2;
import java.util.Scanner;
public class First {
    public static void main(String[] args) {
        Scanner scanner = new Scanner(System.in);
        char c1 = scanner.nextLine().charAt(0);
        char c2 = scanner.nextLine().charAt(0);
        if(((c1>'a'&&c1<'z')||(c1>'A'&&c1<'Z'))&&((c2>'a'&&c2<'z')||(c2>'A'&&c2<'Z'))){
            char min = c1 < c2 ? c1:c2;
            char max = c1 > c2 ? c1:c2;
            for(char c =(char)(min+1);c<max;c++)
                if((c>='a'&&c<='z')||(c>='A'&&c<='Z'))
                    System.out.println(c);
        }
        else
            System.out.println("输入有误！");
    }
}

　　2.输出斐波那契数列的前30位。

package day2;
public class First {
    public static void main(String[] args) {
        int num1 = 1;
        int num2 = 1;
        System.out.println(num1);
        System.out.println(num2);
        for (int i = 0; i < 28; i++) {
            int num =num1+num2;
            System.out.println(num);
            num1 = num2;
            num2 = num;
        }
    }
}

　　3.设计一个方法，计算一个正整数的二进制原码。

package day2;
import java.util.Scanner;
public class First {
    public static void main(String[] args) {
        Scanner scanner = new Scanner(System.in);
        int a = scanner.nextInt();
        String str ="";
        for (int last=a;last != 0;last=last/2){
            str = last%2+str;
        }
        System.out.println(str);
    }
}

　　4.从控制台输入一个数字，判断一个数字是不是回文数。

 

 

二.练习题

　　1.百元百鸡的问题　　

package day2;
public class First {
    public static void main(String[] args) {
        for (int number1 = 0; number1 < 20; number1++) {
            for (int number2 = 0; number2 < 34; number2++) {
                for (int number3 = 0; number3 < 100; number3++) {
                    if((number1+number2+number3*3 == 100)){
                        double money1 = number1*5;
                        double money2 = number2*3;
                        double money3 = number3;
                        if((money1+money2+money3) == 100){
                            System.out.println("母鸡有"+number1 + "公鸡有"+number2 + "小鸡有"+number3*3);
                        }
                    }
                }
            }
        }
    }
}

三.注意事项

　　1.break,continue只对当前的循环生效

　　2.嵌套：外层>>控制行，内层>>控制列

　　3.for和while的使用场景

　　　　(1).当循环次数是可预期的时候，使用for循环。

　　　　(2).当循环次数是不可预期的，但知道循环的条件，使用while循环。

　　4.do-while在条件不成立的时候比while多执行一次循环体。

　　5.break,用在循环中，表示跳出循环。无论循环条件是否成立，这个循环都需要结束。

 

四.方法

 

 

 

 

 五.作业

1.(1)

package day2;
public class First {
    public static void main(String[] args) {
        for (int i = 0; i < 5; i++) {
            switch (i){
                case 1:{
                    System.out.print(" ");
                    break;
                }
                case 2:{
                    System.out.print("  ");
                    break;
                }
                case 3:{
                    System.out.print("   ");
                    break;
                }
                case 4:{
                    System.out.print("    ");
                    break;
                }
            }
            System.out.println("*****");
        }
    }
}

1.(2)

package day2;
public class First {
    public static void main(String[] args) {
        for (int i = 0; i < 5; i++) {
            for (int j = i; j < 9 - i; j++) {
                if(j==i&&i!=0){
                    if(i==1)
                        System.out.print(" ");
                    else if(i==2)
                        System.out.print("  ");
                    else if(i==3)
                        System.out.print("   ");
                    else
                        System.out.print("    ");
                }
                System.out.print("*");
            }
            System.out.println();
        }
    }
}

1(3).

package day2;
public class First {
    public static void main(String[] args) {
        char a ='A';
        for (int i = 0; i < 5; i++) {
            switch(i) {
                case 0: {
                    System.out.print(a);
                    System.out.print((char) (a + 1));
                    System.out.print((char) (a + 2));
                    System.out.print((char) (a + 3));
                    System.out.print((char) (a + 4));
                    break;
                }
                case 1: {
                    a = (char) (a + i);
                    System.out.print(" " + a);
                    System.out.print((char) (a + 1));
                    System.out.print((char) (a + 2));
                    System.out.print((char) (a + 3));
                    System.out.print((char) (a + 4));
                    break;
                }
                case 2: {
                    a = (char) (a + i);
                    System.out.print("  " + a);
                    System.out.print((char) (a + 1));
                    System.out.print((char) (a + 2));
                    System.out.print((char) (a + 3));
                    System.out.print((char) (a + 4));
                    break;
                }
                case 3: {
                    a = (char) (a + i);
                    System.out.print("   " + a);
                    System.out.print((char) (a + 1));
                    System.out.print((char) (a + 2));
                    System.out.print((char) (a + 3));
                    System.out.print((char) (a + 4));
                    break;
                }
                case 4: {
                    a = (char) (a + i);
                    System.out.print("    " + a);
                    System.out.print((char) (a + 1));
                    System.out.print((char) (a + 2));
                    System.out.print((char) (a + 3));
                    System.out.print((char) (a + 4));
                    break;
                }
            }
            a='A';
            System.out.println();
        }
    }
}

1.(4)

public class First {
    public static void main(String[] args) {
        char a ='A';
        for (int i = 0; i <5; i++) {
            switch(i) {
                case 0: {
                    a = (char) (a + 4-i);
                    System.out.print("    " + a);
                    System.out.print((char) (a + 1));
                    System.out.print((char) (a + 2));
                    System.out.print((char) (a + 3));
                    System.out.print((char) (a + 4));
                    break;
                }
                case 1: {
                    a = (char) (a + 4-i);
                    System.out.print("   " + a);
                    System.out.print((char) (a + 1));
                    System.out.print((char) (a + 2));
                    System.out.print((char) (a + 3));
                    System.out.print((char) (a + 4));
                    break;
                }
                case 2: {
                    a = (char) (a + 4-i);
                    System.out.print("  " + a);
                    System.out.print((char) (a + 1));
                    System.out.print((char) (a + 2));
                    System.out.print((char) (a + 3));
                    System.out.print((char) (a + 4));
                    break;
                }
                case 3: {
                    a = (char) (a + 4-i);
                    System.out.print(" " + a);
                    System.out.print((char) (a + 1));
                    System.out.print((char) (a + 2));
                    System.out.print((char) (a + 3));
                    System.out.print((char) (a + 4));
                    break;
                }
                case 4: {
                    System.out.print(a);
                    System.out.print((char) (a + 1));
                    System.out.print((char) (a + 2));
                    System.out.print((char) (a + 3));
                    System.out.print((char) (a + 4));
                    break;
                }
            }
            a='A';
            System.out.println();
        }
    }
}

2.

package day2;
public class First {
    public static void main(String[] args) {
        for (int i = 2; i < 100; i++) {
            for (int j = 2; j < i;j++) {
                if (i%j==0){
                    System.out.println(i+"不是质数");
                    break;
                }
            }
        }
    }
}

3.

package day2;
public class First {
    public static void main(String[] args) {
        for (int i = 1000; i < 9999; i++) {
            int b= i%1000;
            if(i==b*3)
                System.out.println(i);
        }
    }
}

4.

5.

package day2;
public class Wo {
    public static void main(String[] args) {
        double sum =100;
        double h = 100;
        for (int i = 0; i < 10; i++) {
            h=h/2;
            sum+=(h*2);
        }
        System.out.println(sum);
    }
}