You are confusing the "1000 someObjects" versus "1000 references to someObjects". The array just refers to objects, it doesn't actually "contain them". When you allocate the array, it initially will be the size of 1000 object references and they will be set to null. Does that make sense or do you need more detail? More on reddit.com

I think it's pretty clear you didn't read the FAQ and the sidebar. Please read them before continuing and make sure you understand the bit about coding code on pastebin or http://gist.github.com instead of screenshots. More on reddit.com

You can use the .size() method of your ArrayList https://docs.oracle.com/javase/7/docs/api/java/util/ArrayList.html If you do not need the number of the element and only need the element value then you could skip that and just use the enhanced for statement. https://docs.oracle.com/javase/tutorial/java/nutsandbolts/for.html More on reddit.com

Think of an array kind of like the cabinets in your kitchen, all in a line. Each cabinet has a specific location in your kitchen. If you were to tell someone where to find the cups when they're over at your house, you might say "They're in the cabinet over the stove, on the left". Your cabinets are used for storage of your dishes and other kitchen items, and they can be organized a certain way to make finding what you need easier. A one dimensional array is essentially a line of "cabinets" that you can store data in, where each cabinet has its own index, or location, that you reference it by. An array can be unsorted or sorted, and many algorithms exist to sort them, with some being fast, and some requiring very little extra memory. Something like .length or .size simply returns the amount of cabinets in your kitchen, or in programming terms, the number of spaces in your array. You can also make a two dimensional array, which you can think of like a grid of cubby holes at a pre-school, or more mathematically, as a matrix. These work exactly the same as a 1D array, but each element has two indexes instead of one, like an X and Y coordinate on graph paper. An array is stored linearly in memory and its indexes usually start at zero. The following example is how to create an array and fill it with numbers using Java. int[] myArray = new int[10]; //Creates an array of size 10 to store integers for(int i = 0; i < myArray.length; i++) { myArray[i] = i; } //myArray.length = 10, i = 0, loop until i > 9 //On each iteration, myArray at index i will contain the current value of i //When this loop finishes, myArray will contain 0,1,2,3,4,5,6,7,8,9 in that order Arrays are the simplest data structure you will be dealing with, but they are incredibly useful and have a huge amount of applications. Many complex data structures use arrays in some way. For example, you can represent a graph structure as a matrix, or two dimensional array, of connected edges. You can efficiently sort data without using any extra memory using a heap structure, which at its most basic form is just an array that can be sorted in place. Once you grasp arrays, you will be able to grasp the more complex structures much more easily. If there is anything else I can help you with, please let me know. More on reddit.com