搜索数组并返回索引（如果找到特定值）

Question

This is more of just a syntax error, as most of my code as it is runs perfectly fine. The issue is that if a value is not found within the array, I'd like the program to print it out. Can't seem to find a place to write that part of code without the program writing out "Not found" on every line. Below is my code and console output. Thanks all.

Code:

 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);
          }
      }
  }

Console Output:

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

You should use a variable inside the for loop to tell if something was found, also you should exit for once you found something to avoid unnecesary search.

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");    
  }
}

Also, you can read this to learn some other ways to achieve array item searching: 4 ways to search object in array

Answer 2

A quick fix would be the following:

• Add a boolean variable

• Set the boolean variable to true if the element is found

• Write Not Found if the element is not found (ie the boolean variable is false)

PS: Don't forget to make the boolean to false before each loop

Answer 3

Use this after System.out.print("\\nIs " + target + " in the array? "); :

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);
}

Answer 4

There are many ways of doing that, all works well...

Here a example of how you can do:

    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);
    }

Another way is using a boolean to set if was found:

    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);
    }