Implementation of a stack and queue with an array in pseudocode: PostScript and PDF
Implementation of a vector and list with an array in pseudocode: PostScript and PDF
Implementation of a stack, queue and deque with linked lists in pseudocode: PostScript and PDF
How the variables represent the data structure is captured by the (class) invariant. It is an assertion which should hold after initialization and which should be preserved by the operations on the data structure.
To visualize how Java objects are used to implement data structures like stacks and queues you may want to use the Java package explicar.