Understanding WebElement.findElement() and XPATH - selenium

Question

I want to use the WebElement.findElement() API to locate a node inside the parent node using XPATH //span[#class='child-class']. I thought this would return me the <div> that is inside the parent. However, it is returning me the first one it found in the entire DOM tree. Did I use the wrong XPATH?
I have also tried using .//span[#class='child-class'] as the XPATH, but that does return anything.
Thank you.
UPDATE:
given the HTML below, I want to define a locator for the child-title <span> and child-date <span> and locate them using WebElement.findElement() API regardless of the parent being "//a/li[1]" or "//a/li[2]"
<a>
<li> parent 1
<div>
<span class="child-title child-style">title 1</span>
<span class="child-date child-style"> date 1</span>
<span class="child-author">author 1</span>
</div>
</li>
</a>
<a>
<li> parent 2
<div>
<span class="child-title child-style">title 2</span>
<span class="child-date child-style"> date 2</span>
<span class="child-author">author 3</span>
</div>
</li>
</a>
<a>
<li> parent 3
<div>
<span class="child-title child-style">title 3</span>
<span class="child-date child-style"> date 3</span>
<span class="child-author">author 3</span>
</div>
</li>
</a>
I have a WebElement parent2 initialized and located using "//a/li[2]",
WebElement child = parent2.findElement(By.xpath("//span[#class='child-author']")); would give me "author 1"
WebElement child = parent2.findElement(By.xpath("span[#class='child-author']")); would give me NoSuchElementException

Answer 1

There are my 2 comments with your sample code
1 - With your posted HTML, the xpath //a/li[2] is not found (we only have 3 elements with //a/li[1])
2 - Assume that we do have right code, you need to understand the differences between single slash and double slash in Xpath
a/b (single slash): select element that has "tag b" and "stands right after" an element that has "a tag"
E.g.:
<a>
<b>
<d>
<c>
</c>
</d>
</b>
</a>
AND
a//b (double slash): select element that has "tag b" and is n-level-child an element that has "a tag"
E.g.:
<a>
<c>
<d>
<b>
</b>
</d>
</c>
</a>
So, with your code
<a>
<li> parent 1
<div>
<span class="child-title child-style">title 1</span>
<span class="child-date child-style"> date 1</span>
<span class="child-author">author 1</span>
</div>
</li>
</a>
If you want to get Date Info, you should use
WebElement parent = driver.findElement(By.xpath("//a/li"));
WebElement date = parent.findElement(By.xpath("div/span[contains(#class, 'child-date')]"));
WebElement date = parent.findElement(By.xpath("//span[contains(#class, 'child-date')]"));
The code
WebElement date = parent.findElement(By.xpath("span[contains(#class, 'child-date')]"));
Will bring out NoSuchElementException because there is no [span] tag right after [li] tag
Hope help

Answer 2

Try something like:
Use dot(.) before double slash(//)
It looks for child under the given parent element.

Answer 3

Completely new question ... completely new answer. :(
Try something like:
WebElement parent1 = driver.findElement(By.xpath("//a[1]/li")); // use a[2] for parent2
WebElement author = parent1.findElement(By.xpath("span[#class='child-author']"));
WebElement date = parent1.findElement(By.xpath("span[contains(#class, 'child-date')]"));
WebElement title = parent1.findElement(By.xpath("span[contains(#class, 'child-title')]"));

Answer 4

Try something like :
//a/li[contains(text(), 'parent 1')]/div
It requests for "the <div> inside a <li> whose text contains 'parent 1' and who is inside a <a>.
It might not work if you have more parents because it works with a contains() (this xpath would also select <li> parent 10 ... </li>). It would be better if "parent x" were an attribute of the <li> instead of its text.