第七章编程作业

1. 数组查找操作

定义一个长度为10 的一维字符串数组,在每一个元素存放一个单词;然后运行时从命令行输入一个单词,
程序判断数组是否包含有这个单词,包含这个单词就打印出“Yes”,不包含就打印出“No”.

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import java.util.*;

public class ArraySearch {
	public static void main(String[] args) {
		String[] s;
		s = new String[]{"hello","world","right","red","pink","food","big","boom","trace","fly"};
		Scanner scan = new Scanner(System.in);
		String inName = scan.nextLine();
		searchStr(s,inName);
	}
	
	public static void searchStr(String[] s, String str) {
		for(String ss: s) {
			if(str.equals(ss)){
				System.out.print("yes");
				return;
			}
		}
		System.out.print("no");
	}
}    

2. 获取数组最大值和最小值操作

利用Java的Math类的random()方法,编写函数得到0到n之间的随机数,n是参数.并找出产生50个这样的随机数中最大的、最小的数,
并统计其中>=60的有多少个.


提示：使用 int num=(int)(n*Math.random());获取随机数.
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import java.io.IOException;
import java.util.Scanner;

public class MaxAndMinValue {

	public static void main(String[] args) throws IOException {
		Scanner scan = new Scanner(System.in);
		int n = scan.nextInt();
		acquireNum(n);
	}
	
	public static void acquireNum(int n) {
		int a[] = new int[50];
		for(int i=0;i<a.length;i++) {
			a[i] = (int)(Math.random() * n + 1);
		}
		
		int max=a[0];
		int min=a[0];
		int number = 0;
		for (int i : a) {
			if(i>=60) {
				number++;
			}
			if(max<i) {
				max = i;
			}
			if(min>i) {
				min = i;
			}
		}
		System.out.println("Those max is : " + max);
		System.out.println("Those min is : " + min);
		System.out.println("More than the 60 numbers : " + number);
		
	}
	
}

3. 数组逆序操作

定义长度为10的数组,将数组元素对调,并输出对调前后的结果.

思路：把0索引和arr.length-1的元素交换,把1索引和arr.length-2的元素交换…..

只要交换到arr.length/2的时候即可. 
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import java.util.Arrays;

public class NumExchange {
	
	public static void main(String[] args) {
		
		int a[] = {2,4,5,6,7,8,234,23,12,54};
		exchangeElement(a);
	}
	
	public static int[] exchangeElement(int[] a) {
		int t;
		int len = a.length;
		
		for(int i=0;i<=(len-1)/2;i++) {
			t = a[i];
			a[i] = a[len-i-1];
			a[len-i-1] = t;
		}
		
		System.out.print(Arrays.toString(a));
		
		return a;
	}
	
}