Databases
StackOverflow2013
Postsdbo
PO
 

Note that there are some explanatory texts on larger screens.

plurals
  1. PO
    primarykey
    data
    text
    <p>You say this is the line of code causing the exception:</p> <pre><code>while(temp.object.style.compareTo(element.style) &lt;= 0) </code></pre> <p>You probably should set a debugger breakpoint on that line and use a debugger to determine which of the values is null. But it's hard for me to explain here full instructions on how to setup and use a debugger (that doesn't mean you shouldn't learn! You should. There are lots of tutorials. Google it.) So instead of writing a tutorial on debuggers, I'll just post code that will tell you which variable is null:</p> <pre><code>if (temp == null) { System.out.println("temp is null"); } else if (temp.object == null) { System.out.println("temp.object is null"); } else if (temp.object.style == null) { System.out.println("temp.object.style is null"); } if (element == null) { System.out.println("element is null"); } else if (element.style == null) { System.out.println("element.style is null"); } while(temp.object.style.compareTo(element.style) &lt;= 0) //This is where the nullPointerException occurs { if(temp.hasNext()) temp = temp.next; if (temp == null) { System.out.println("loop: temp is null"); } else if (temp.object == null) { System.out.println("loop: temp.object is null"); } else if (temp.object.style == null) { System.out.println("loop: temp.object.style is null"); } if (element == null) { System.out.println("loop: element is null"); } else if (element.style == null) { System.out.println("loop: element.style is null"); } } </code></pre> <p>If you use the above code statements to replace these three lines of your code:</p> <pre><code> while(temp.object.style.compareTo(element.style) &lt;= 0) //This is where the nullPointerException occurs if(temp.hasNext()) temp = temp.next; </code></pre> <p>you will know which variable is null based on which statement is printed. Hopefully you can take it from there. (The usual way to fix a NullPointerException is to take the steps necessary to ensure the offending null variable actually has a valid, non-null value by the time the program reaches the line of the NullPointerException).</p>
    singulars
    1. This table or related slice is empty.
    1. PONullPointerException with while loop using compareTo
      singulars
      1. PTQuestion
    1. PTAnswer
    1. USMike Clark
    1. USMike Clark
    plurals
    1. This table or related slice is empty.
    1. This table or related slice is empty.
    1. This table or related slice is empty.
    1. This table or related slice is empty.
    1. VO
      singulars
      1. PO
      1. This table or related slice is empty.
      1. VTUpMod
    2. VO
      singulars
      1. PO
      1. This table or related slice is empty.
      1. VTUpMod
    1. CONice answer. But maybe a little cruel...
      singulars
      1. PO
      1. USRadu Murzea
    2. COThe thing is, I just put this all in a try-catch and even though it throws an exception, the code in the while-loop works. I also tried to check for "temp == null" and nothing printed out.
      singulars
      1. PO
      1. USprunes4u
    3. COI fixed it. For some reason the code runs fine but the NullPointerException is thrown. I just took out the stack trace and it prints out the information just as I want it.
      singulars
      1. PO
      1. USprunes4u
 

Querying!

 
Guidance
A row detail

Detail views are divided into sections. All the information in the data section comes from columns in the selected row. The other sections display data from other, related rows.

Related data can be related in a to-one or a to-many fashion. Captions of data related in a to-many fashion link to a list view showing a filtered view of the table.

Try moving around until you find a non-empty to-many entry and click on the label to get to one. You can move back to the root by clicking on the database name in the header.

SQuiL has stopped working due to an internal error.

If you are curious you may find further information in the browser console, which is accessible through the devtools (F12).

Reload