java答案2

选择

DDBDB BDCAA ADAAA

填空

4-1
BufferedInputStream

4-2
OutputStream
Reader

程序填空题

5-1
throw new
IllegalAccessException e

5-2
int t a
t

5-3
f[i]=f[i-1]+f[i-2]
int i=0
(i+1)%4==0

编程题

7-1

public class Main {
    public static void main(String[] args) {
        Dog animal = new Dog();
        animal.shout();
        animal.run();
    }
}
class Animal {
    void shout() {
        System.out.println("animal shout！");
    }
}
class Dog extends Animal {
    void shout() {
        super.shout();
        System.out.println("wangwang……");
    }

    void run() {
        System.out.println("Dog is running");
    }
}

7-2

public class Main {
    public static void main(String[] args) {
        Son son = new Son();
        son.method();
    }
}
class Parent {
    Parent() {
        System.out.println("Parent's Constructor without parameter");
    }

    Parent(boolean b) {
        System.out.println("Parent's Constructor with a boolean parameter");
    }

    public void method() {
        System.out.println("Parent's method()");
    }
}
class Son extends Parent {
    Son() {
        super(true);
        System.out.println("Son's Constructor without parameter");

    }
    public void method() {
        System.out.println("Son's method()");
        super.method();
    }
}

7-3

import java.util.Scanner;
public class Main{

    public static void main(String[] args) {
        Scanner in=new Scanner(System.in);
        int n=in.nextInt();
        int sum1=0,sum2=0;
        int []s=new int[n];
        for(int i=0;i<n;i++) {
            int m=in.nextInt();
            if(m>100||m<0) {
                System.out.println(m+"invalid!");
                i--;
                continue;
            }
            else
                s[i]=m;
            if(m<60) sum1+=1;
            else sum2+=1;
        }
        System.out.println(sum2);
        System.out.println(sum1);
    }

}

7-4

import java.util.Arrays;
import java.util.Scanner;
class Main {
    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        int n = sc.nextInt();
        int[] arr = new int[n];
        for (int i = 0; i < n; i++) {
            arr[i] = sc.nextInt();
        }
        double sum = 0;
        for (int i = 0; i < n; i++) {
            sum += arr[i];
        }
        double mean = sum / n;
        arr = Arrays.stream(arr).sorted().toArray();
        double median = 0;
        if (n % 2 == 0) {
            median = (arr[n / 2 - 1] + arr[n / 2]) / 2.0;
        }
        else {
            median = arr[n / 2];
        }
        System.out.print("mean=" + String.format("%.2f", mean) + ",median=" + String.format("%.1f", median));
    }
}

7-5

import java.util.Arrays;
import java.util.Scanner;
public class Main {
    public static void main(String[] args) {
        Scanner scanner = new Scanner(System.in);
        int n = scanner.nextInt();
        int[] arr = new int[n];
        for (int i = 0; i < n; i++) {
            try{
                String str = scanner.next();
                arr[i] = Integer.parseInt(str);
            }catch (Exception e){
                System.out.println(e);
                i--;
            }
        }
        System.out.println(Arrays.toString(arr));
    }
}