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exercism fetch java circular-buffer

Circular Buffer

A circular buffer, cyclic buffer or ring buffer is a data structure that uses a single, fixed-size buffer as if it were connected end-to-end.

A circular buffer first starts empty and of some predefined length. For example, this is a 7-element buffer:

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[ ][ ][ ][ ][ ][ ][ ]

Assume that a 1 is written into the middle of the buffer (exact starting location does not matter in a circular buffer):

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[ ][ ][ ][1][ ][ ][ ]

Then assume that two more elements are added — 2 & 3 — which get appended after the 1:

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[ ][ ][ ][1][2][3][ ]

If two elements are then removed from the buffer, the oldest values inside the buffer are removed. The two elements removed, in this case, are 1 & 2, leaving the buffer with just a 3:

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[ ][ ][ ][ ][ ][3][ ]

If the buffer has 7 elements then it is completely full:

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[6][7][8][9][3][4][5]

When the buffer is full an error will be raised, alerting the client that further writes are blocked until a slot becomes free.

When the buffer is full, the client can opt to overwrite the oldest data with a forced write. In this case, two more elements — A & B — are added and they overwrite the 3 & 4:

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[6][7][8][9][A][B][5]

3 & 4 have been replaced by A & B making 5 now the oldest data in the buffer. Finally, if two elements are removed then what would be returned is 5 & 6 yielding the buffer:

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[ ][7][8][9][A][B][ ]

Because there is space available, if the client again uses overwrite to store C & D then the space where 5 & 6 were stored previously will be used not the location of 7 & 8. 7 is still the oldest element and the buffer is once again full.

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[D][7][8][9][A][B][C]

Running the tests

You can run all the tests for an exercise by entering

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$ gradle test

in your terminal.

Source

Wikipedia http://en.wikipedia.org/wiki/Circular_buffer

Submitting Incomplete Solutions

It's possible to submit an incomplete solution so you can see how others have completed the exercise.