JAVA基础学习（5）之数组

5数组

5.1数组

5.1.1初识数组

 1 //        输出大于平均数的所有数
 2         Scanner in = new Scanner(System.in);
 3         int n;
 4         int[] a = new int[100];
 5         int count = 0;
 6         double sum = 0;
 7         while ((n = in.nextInt()) != -1)
 8         {
 9             a[count] = n;
10             sum += n;
11             count++;
12         }
13         if (count > 0)
14         {
15 
16             for (int i = 0; i < count; i++)
17             {
18                 if (a[i] > (sum / count))
19                 {
20                     System.out.println(a[i]);
21                 }
22             }
23             System.out.println("平均数为：" + sum / count);
24         }

5.1.2创建数组
5.1.3数组的元素
- 数组的大小不能改变

5.1.4数组变量

普通变量所有者
数组变量管理者

 1 int[] a = new int[10];
 2         a[0] = 5;
 3         int[] b = a;
 4         System.out.println(a[0]);
 5         System.out.println(b[0]);
 6         for (int i = 0; i < b.length; i++)
 7         {
 8             if (i == b.length - 1)
 9             {
10                 System.out.println(b[i]);
11                 break;
12             }
13             System.out.print(b[i]);
14         }
15         System.out.println(a);
16         System.out.println(b);

5.2数组计算

5.2.1投票统计

 1 // 投票统计
 2         Scanner in = new Scanner(System.in);
 3         int x;
 4         int[] numbers = new int[10];
 5         while ((x = in.nextInt()) != -1)
 6         {
 7             if ((x >= 0) && (x <= 9))
 8             {
 9                 numbers[x]++;
10             }
11         }
12         for (int i = 0; i < numbers.length; i++)
13         {
14             System.out.println(i + ": " + numbers[i]);
15         }

5.2.2遍历数组

 1 // 遍历数组
 2         Scanner in = new Scanner(System.in);
 3         int x = in.nextInt();
 4         int[] a =
 5         { 3, 4, 5, 6, 7, 8, 32, 45 };
 6         int loc = -1;
 7         boolean flag = false;
 8         for (int i = 0; i < a.length; i++)
 9         {
10             if (x == a[i])
11             {
12                 loc = i;
13                 break;
14             }
15         }
16         for (int k : a)
17         {
18             if (k == x)
19             {
20                 flag = true;
21             }
22         }
23         if (flag)
24         {
25             System.out.println(x + "存在");
26             System.out.println(x + "在第" + (loc + 1) + "个");
27         } else
28         {
29             System.out.println(x + "不在其中");
30         }

5.2.3素数

 1 // 素数
 2         Scanner in = new Scanner(System.in);
 3         System.out.println("请输入一个数：");
 4         int x = in.nextInt();
 5         boolean isPrime = true;
 6         if (x == 1 || x % 2 == 0 && x != 2)
 7         {
 8             isPrime = false;
 9         } else
10         {
11             for (int i = 3; i < Math.sqrt(x); i+=2)
12             {
13                 if (x%i==0)
14                 {
15                     isPrime=false;
16                     break;
17                 }
18             }
19         }
20         if (isPrime)
21         {
22             System.out.println(x+"是素数");
23         }else
24         {
25             System.out.println(x+"不是素数");
26         }

5.3二维数组
- OX棋