Referencing a new library in Eclipse

Please see the attached image:

1) I downloaded a new library here: (http://www.java2s.com/Code/Jar/ABC/Downloadcommonslang24jar.htm)

2) In Eclipse, I right-clicked on 'Referenced Libraries' > Build Path > Configure Build Path > Add External JARs and added 'commons-lang-2.4.jar'

3) I've added import org.apache.commons.lang.* at the top of my class.

4) I entered a method from that class indexOfAny() and get the following error: 'The method indexOfAny() is undefined for the type 开发者_C百科String.'

What step(s) am I missing? Which steps that I've taken are unnecessary? I need to be able to use this method.

P.S. Pls ignore the rest of the code.

indexOfAny() is NOT a method on a String object.

Maybe you meant to write StringUtils.indexOfAny(...)

You're not using it right, you're trying to invoke the method indexOfAny() on a java.lang.String object - this method is not part of that class. You need to call these methods statically on org.apache.commons.lang.StringUtils - something of the form StringUtils.XXX()

The Commons Library doesn't augment existing classes (in any case, java.lang.String is final). According to the documentation, your call should be something that looks like:

StringUtils.indexOfAny(quantityInForPriceBandPopUp[i], ['z'])

or using one of the overloaded versions.

Update

Is importing the package necessary?

This article and the Java package trail should help with all the details of packages and imports. But some of the basic things to understand are :

1. Packages are the namespacing mechanism that Java uses - this allows you and I both to write a Utils class while avoiding a collision because of the same name. For example, java.sql.Date and java.util.Date - two Date classes can exist and be used because they're in different packages. It might help to envision packages and their sub-packages as a hierarchy of folders.

2. Imports are a convenience feature that lets you reference classes by their simple name (Math or String) instead of their fully qualified name (FQN) (java.lang.Math or java.lang.String) every single time you want to use it, which gets painful and clutters up your code, making it much less readable.

3. Imports don't add anything to your code or make it less efficient since the imported packages aren't linked to your code or anything like that - as mentioned above, it's simply a way to avoid having to use the FQN all the time.

So to answer your question, no, the import is not necessary but then you'd have to use org.apache.commons.lang.StringUtils every single time instead of just being able to use StringUtils. So while not necessary, it's usually convenient both for yourself and anyone else who's going to try to read your code.

You are trying to use these methods on Strings, you should read the documentation of the library you want to use.

Because in documentation you have:

static int indexOfAny(String str, char[] searchChars)

1. static == you should call this method like this: StringUtils.indexOfAny(...)
2. String str == put your string here
3. char[] searchChars == put array of chars which you're searching

Search a String to find the first index of any character in the given set of characters.