SDK version: 4.6.00 java stacktrace: java.lang.NullPointerException: Attempt to invoke virtual method 'boolean java.lang.String.contains (java.lang.CharSequence)' on ...

Java Check String for Number This small program can be used to determine if a string contains numbers. This is useful for programs that want only number input from the user and Try Catch or for what ...

One of the nasty little traps a Java developer can run into occurs when Collection.contains(Object) is not used with appropriate understanding. I demonstrate this potential trap in this post.