First, what is an array? An array, in the IT world, is basically a collection of elements that are the same as one another with the collection itself identified with a special or unique identifier. These elements under the same collection batch are situated in contiguous memory spaces.
The advantage with using an array is that there is no need to identify and tag each individual element with its own special or unique identifier. The array itself will have its own special or unique identifier. The first element (called an index in the world of arrays) will always have a value of zero regardless of how long that index is.
Now, used in the world of SCJP 1.5, you may find that the SCJP 1.5 exam requires knowledge of arrays. You can see in the Exam Objectives in Section 1 that the examinee is required to declare and produce an array, initialize it, and then employ that same array as variables that are local, instance and static through the codes written by the examinee.
Apparently, arrays come into the picture in Section 1 because they make up one of the most basic concepts in the SCJP accreditation world.
One tip you need to acknowledge is that SCJP 1.5 is harder than SCJP 1.4 in general. To understand arrays and how they help you in the SCJP 1.5 world, do not rely on braindumps which just require route memorization. Rather, aim for understanding how arrays fit into the grand scheme of the SCJP 1.5 system and emphasize knowing how to write code for arrays too.