JAVA基础学习（5）之数组

5数组

• 5.1数组
  • 5.1.1初识数组
    • 　　

      //        输出大于平均数的所有数
              Scanner in = new Scanner(System.in);
              int n;
              int[] a = new int[100];
              int count = 0;
              double sum = 0;
              while ((n = in.nextInt()) != -1)
              {
                  a[count] = n;
                  sum += n;
                  count++;
              }
              if (count > 0)
              {
      
                  for (int i = 0; i < count; i++)
                  {
                      if (a[i] > (sum / count))
                      {
                          System.out.println(a[i]);
                      }
                  }
                  System.out.println("平均数为：" + sum / count);
              }

  • 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

    • int[] a = new int[10];
              a[0] = 5;
              int[] b = a;
              System.out.println(a[0]);
              System.out.println(b[0]);
              for (int i = 0; i < b.length; i++)
              {
                  if (i == b.length - 1)
                  {
                      System.out.println(b[i]);
                      break;
                  }
                  System.out.print(b[i]);
              }
              System.out.println(a);
              System.out.println(b);

• 5.2数组计算
  • 5.2.1投票统计
    • 　　

      // 投票统计
              Scanner in = new Scanner(System.in);
              int x;
              int[] numbers = new int[10];
              while ((x = in.nextInt()) != -1)
              {
                  if ((x >= 0) && (x <= 9))
                  {
                      numbers[x]++;
                  }
              }
              for (int i = 0; i < numbers.length; i++)
              {
                  System.out.println(i + ": " + numbers[i]);
              }

  • 5.2.2遍历数组
    • 　　

      // 遍历数组
              Scanner in = new Scanner(System.in);
              int x = in.nextInt();
              int[] a =
              { 3, 4, 5, 6, 7, 8, 32, 45 };
              int loc = -1;
              boolean flag = false;
              for (int i = 0; i < a.length; i++)
              {
                  if (x == a[i])
                  {
                      loc = i;
                      break;
                  }
              }
              for (int k : a)
              {
                  if (k == x)
                  {
                      flag = true;
                  }
              }
              if (flag)
              {
                  System.out.println(x + "存在");
                  System.out.println(x + "在第" + (loc + 1) + "个");
              } else
              {
                  System.out.println(x + "不在其中");
              }

  • 5.2.3素数
    • 　　

      // 素数
              Scanner in = new Scanner(System.in);
              System.out.println("请输入一个数：");
              int x = in.nextInt();
              boolean isPrime = true;
              if (x == 1 || x % 2 == 0 && x != 2)
              {
                  isPrime = false;
              } else
              {
                  for (int i = 3; i < Math.sqrt(x); i+=2)
                  {
                      if (x%i==0)
                      {
                          isPrime=false;
                          break;
                      }
                  }
              }
              if (isPrime)
              {
                  System.out.println(x+"是素数");
              }else
              {
                  System.out.println(x+"不是素数");
              }

• 5.3二维数组
  • OX棋