How arrays and collections are similar

• Like an array, a collection is an object that can store multiple occurrences of other objects.
• Some collection types (such as ArrayList) use arrays internally to store data.
• An array is a Java language feature. Collections are classes in the Java API.
• Collection classes have methods that perform operations that arrays don't provide.
• Arrays are fixed in size. Collections are variable in size.
• Arrays can store primitive types. Collections can't.
• Indexes are almost always required to process arrays. Collections are usually processed without using indexes.

Code that uses an array

String[] codes = new String[3];
codes[0] = "mcb2";
codes[1] = "java";
codes[2] = "jsps";
for (int i = 0; i < codes.length; i++)
    System.out.println(codes[i]);

Code that uses a collection

ArrayList<String> codes = new ArrayList<String>();
codes.add("mcb2");
codes.add("java");
codes.add("jsps");
for (String s : codes)
    System.out.println(s);