JAVA基础学习之数组

Posted 2020-11-24 生长的力量

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