how to fix contains method with generics

Question

My contains method works properly for smaller indices but then for big indices such as the test cases 1000, 2000, 2999 it does not work. I do not see why. I checked the output for the print statement in the loop which shows that the numbers I am checking for are present in the object array.

Assume the objects in array and element are int. data is Object []

public boolean contains(E element) {
         boolean flag = false;
         if (this.size() == 0) { return flag;}

         for (int i = 0; i < this.data.length; i++) {
              if (element == this.data[i]) { flag = true; }
              System.out.println(this.data[i]);
         }
         return flag;
}

@Test
public void mustGrowArray()  {
      OurSet<Integer> ints = new ArraySet<Integer>();
      for (int i = 0; i < 3000; i++) {
        ints.add(i);
      }
      assertEquals(3000, ints.size());//passes
      assertTrue(ints.contains(1000));// fails
      assertTrue(ints.contains(2000));// fails
      assertTrue(ints.contains(2999));// fails
}

You can have two objects that are .equals but not equal. Eg. `Integer a = new Integer(1); Integer b = new Integer(1);` a==b is false, but a.equals(b) is true. I'm surprised 1000 isn't cached when it is autoboxed. — matt, Jun 26 '19 at 06:21
Another suggestion: instead of: flag=true you should return true; or break; just after -> it's faster as you don't need to check all the array — NikNik, Jun 26 '19 at 06:29

score 1 · Answer 1 · answered Jun 26 '19 at 06:19

1

== is not .equals!

Use .equals instead in this line,

if (element == this.data[i])

to

if (element.equals(this.data[i]))

Hope it helps.

answered Jun 26 '19 at 06:19

Himanshu Bhardwaj

4,038
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score 0 · Answer 2 · edited Jun 26 '19 at 07:45

0

Compare with equals instead of ==

use this `for-loop:

for (int i = 0; i < this.data.length; i++) {
    if (element.equals(this.data[i])) {
       flag = true;
    }
    System.out.println(this.data[i]);
}

To know the differences between equals and == operator go through this link: Difference between "equals" and "==" operator

edited Jun 26 '19 at 07:45

Zain Arshad

1,885
1
11
26

answered Jun 26 '19 at 06:52

how to fix contains method with generics

2 Answers2