Databases
StackOverflow2013
Postsdbo
POUnknown NullPointerException in Java
 

Note that there are some explanatory texts on larger screens.

plurals
  1. POUnknown NullPointerException in Java
    primarykey
    data
    text
    <p>The following snippet uses simple Java code.</p> <pre><code>package pkg; final public class Main { final private class Demo { private Integer value = null; public Integer getValue() { return value; } } private Integer operations() { Demo demo = new Demo(); return demo==null?new Integer(1):demo.getValue(); } public static void main(String[] args) { Main main=new Main(); System.out.println("Value = " + String.valueOf(main.operations())); } } </code></pre> <p>The above code works as expected with no problem and displays <code>Value = null</code> on the console.</p> <p>In the following <code>return</code> statement,</p> <pre><code>return demo==null?new Integer(1):demo.getValue(); </code></pre> <p>since the object <code>demo</code> of type <code>Demo</code> is <strong>not</strong> <code>null</code>, the expression after <code>:</code> which is <code>demo.getValue()</code> is executed which invokes <code>getValue()</code> within the inner <code>Demo</code> class which returns <code>null</code> and finally, it is converted to String and displayed on the console.</p> <p>But when I modify the <code>operations()</code> method something like the one shown below,</p> <pre><code>private Integer operations() { Demo demo = new Demo(); return demo==null?1:demo.getValue(); } </code></pre> <p>it throws <code>NullPointerException</code>. How?</p> <hr> <p>I mean when I use this <code>return</code> statement </p> <pre><code>return demo==null?new Integer(1):demo.getValue(); </code></pre> <p>it works (doesn't throw <code>NullPointerException</code>)</p> <p>and when I use the following <strong>something similar</strong> <code>return</code> statement</p> <pre><code>return demo==null?1:demo.getValue(); </code></pre> <p>it causes <code>NullPointerException</code>. Why?</p>
    singulars
    1. PO
      singulars
      1. PTAnswer
    1. This table or related slice is empty.
    1. PTQuestion
    1. USLion
    1. USLion
    plurals
    1. PL
      singulars
      1. LTLinked
    1. This table or related slice is empty.
    1. This table or related slice is empty.
    1. PO
      singulars
      1. PTAnswer
    2. PO
      singulars
      1. PTAnswer
    1. VO
      singulars
      1. POUnknown NullPointerException in Java
      1. This table or related slice is empty.
      1. VTUpMod
    2. VO
      singulars
      1. POUnknown NullPointerException in Java
      1. This table or related slice is empty.
      1. VTUpMod
    3. VO
      singulars
      1. POUnknown NullPointerException in Java
      1. This table or related slice is empty.
      1. VTUpMod
    1. COhttp://stackoverflow.com/questions/7811608/java-npe-in-ternary-operator-with-autoboxing
      singulars
      1. POUnknown NullPointerException in Java
      1. USPetteri Hietavirta
    2. COpossible duplicate of [strange Java NullPointerException with autoboxing](http://stackoverflow.com/questions/3265948/strange-java-nullpointerexception-with-autoboxing)
      singulars
      1. POUnknown NullPointerException in Java
      1. USPops
 

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