How to convert Integer to int?

Question

As already written elsewhere:

• For Java 1.5 and later you don't need to do (almost) anything, it's done by the compiler.
• For Java 1.4 and before, use Integer.intValue() to convert from Integer to int.

BUT as you wrote, an Integer can be null, so it's wise to check that before trying to convert to int (or risk getting a NullPointerException).

pstmt.setInt(1, (tempID != null ? tempID : 0));  // Java 1.5 or later

or

pstmt.setInt(1, (tempID != null ? tempID.intValue() : 0));  // any version, no autoboxing  

^*using a default of zero, could also do nothing, show a warning or ...

I mostly prefer not using autoboxing (second sample line) so it's clear what I want to do.

Since you say you're using Java 5, you can use setInt with an Integer due to autounboxing: pstmt.setInt(1, tempID) should work just fine. In earlier versions of Java, you would have had to call .intValue() yourself.

The opposite works as well... assigning an int to an Integer will automatically cause the int to be autoboxed using Integer.valueOf(int).

Java converts Integer to int and back automatically (unless you are still with Java 1.4).

Another simple way would be:

Integer i = new Integer("10");

if (i != null)
    int ip = Integer.parseInt(i.toString());