Question

这更像是一个语法错误，因为我的大部分代码运行得非常好。问题是如果在数组中找不到值，我希望程序将其打印出来。在没有程序写出的情况下，似乎找不到编写代码部分的地方＆＃34; Not found＆＃34;在每一行。下面是我的代码和控制台输出。谢谢大家。

代码：

 public static void main(String[ ] args)
 {
  final int[ ] DATA = { 2, 4, 6, 8, 10, 12, 14 };
  final int[ ] EMPTY = new int[0];
  final int MINIMUM = 0;
  final int MAXIMUM = 16;

  int target;

  System.out.println("Searching for numbers in an array.");
  for (target = MINIMUM; target <= MAXIMUM; target++)
  {
      System.out.print("\nIs " + target + " in the array? ");
      {
          for (int index = 0; index < DATA.length; index++)
          {
               if ( DATA[index] == target )
                   System.out.printf("Yes! %d was found at index [%d]", target, index);
          }
      }
  }

控制台输出：

Searching for numbers in an array...

Is 0 in the array? 
Is 1 in the array? 
Is 2 in the array? Yes! 2 was found at index [0]
Is 3 in the array? 
Is 4 in the array? Yes! 4 was found at index [1]
Is 5 in the array? 
Is 6 in the array? Yes! 6 was found at index [2]
Is 7 in the array? 
Is 8 in the array? Yes! 8 was found at index [3]
Is 9 in the array? 
Is 10 in the array? Yes! 10 was found at index [4]
Is 11 in the array? 
Is 12 in the array? Yes! 12 was found at index [5]
Is 13 in the array? 
Is 14 in the array? Yes! 14 was found at index [6]
Is 15 in the array? 
Is 16 in the array?

Answer 1

你应该在for循环中使用一个变量来判断是否找到了某些东西，你也应该在找到一些东西后退出以避免不必要的搜索。

public static void main(String[ ] args)
 {
  final int[ ] DATA = { 2, 4, 6, 8, 10, 12, 14 };
  final int[ ] EMPTY = new int[0];
  final int MINIMUM = 0;
  final int MAXIMUM = 16;
  boolean foundElement;
  int target;

  System.out.println("Searching for numbers in an array.");
  for (target = MINIMUM; target <= MAXIMUM; target++)
  {
      System.out.print("\nIs " + target + " in the array? ");
      foundElement = false;
      for (int index = 0; (index < DATA.length && !foundElement); index++)
       {
             foundElement = (DATA[index] == target);
             if ( foundElement )
               System.out.printf("Yes! %d was found at index [%d]", target, index);                       
        }
        if (!foundElement)
          System.out.printf(" Not found");    
  }
}

另外，您可以阅读本文以了解实现数组项搜索的其他方法：4 ways to search object in array

Answer 2

快速修复如下：

添加布尔变量
如果找到元素，则将布尔变量设置为true
如果找不到元素，则写入未找到（即布尔变量为假）

PS：不要忘记在每个循环之前将布尔值设为假

Answer 3

在boolean found = false; for (int index = 0; index < DATA.length; index++) { if ( DATA[index] == target ) { System.out.printf("Yes! %d was found at index [%d]", target, index); found = true; break; } } if (!found) { System.out.printf("No! %d was not found", target); }：

之后使用此功能

rate

Answer 4

有很多方法可以做到这一点，一切运作良好......

以下是您可以做的一个示例：

    final int[ ] DATA = { 2, 4, 6, 8, 10, 12, 14 };
    final int[ ] EMPTY = new int[0];
    final int MINIMUM = 0;
    final int MAXIMUM = 16;
    int foundIndex;
    int target;

    System.out.println("Searching for numbers in an array.");
    for (target = MINIMUM; target <= MAXIMUM; target++)
    {
        foundIndex = -1;
        System.out.print("\nIs " + target + " in the array? ");
        {
            for (int index = 0; index < DATA.length; index++)
            {
                if ( DATA[index] == target ){
                    foundIndex = index;
                    break;
                }
            }
        }
        if(foundIndex > -1)
            System.out.printf("Yes! %d was found at index [%d]", target, foundIndex);
        else
            System.out.printf("No! %d was not found", target);
    }

另一种方法是使用布尔值设置是否找到了：

    final int[ ] DATA = { 2, 4, 6, 8, 10, 12, 14 };
    final int[ ] EMPTY = new int[0];
    final int MINIMUM = 0;
    final int MAXIMUM = 16;
    boolean found;
    int target;

    System.out.println("Searching for numbers in an array.");
    for (target = MINIMUM; target <= MAXIMUM; target++)
    {
        found = false;
        System.out.print("\nIs " + target + " in the array? ");
        {
            for (int index = 0; index < DATA.length; index++)
            {
                if ( DATA[index] == target ){
                    found = true;
                    System.out.printf("Yes! %d was found at index [%d]", target, index);
                    break;
                }
            }
        }
        if(!found)
            System.out.printf("No! %d was not found", target);
    }

搜索数组并返回索引（如果找到特定值）

4 个答案: