ringbuffer.java

import java.util.Collections;

public class RingBuffer<T> {
	int length;
	int currentPos = 0;
	int firstPos = 0;
	int lastPos;
	private T[] buffer;

	@SuppressWarnings("unchecked")
	public RingBuffer(int length) {
		this.length = length;
		this.lastPos = length-1;
		this.buffer = (T[]) new Object[length];
	}
	
	public void put(T v) {
		buffer[currentPos]=v;
		dumpContent(true,v);
		currentPos++;
		flowPos();
	}
	
	public T pop() {
		currentPos--;
		flowPos();
		T v = buffer[currentPos];
		buffer[currentPos]=null;
		dumpContent(false,v);
		return v;
	}
	
	public void flowPos() {
		if(currentPos<firstPos) {
			currentPos=lastPos;
		}else if(currentPos>lastPos) {
			currentPos=firstPos;
		}
	}
	
	private void dumpContent(boolean put,T v) {
		int spaceCount = 0;
		for (int i = 0; i < buffer.length; i++) {
			String out = "["+i+"] = "+buffer[i]+", ";
			if(i<currentPos) {
				spaceCount+=out.length();				
			}
			System.out.print(out);
		}
		String action = (put?"PUT":"POP")+"="+v;
		System.out.println("\r\n"+String.join("", Collections.nCopies(spaceCount, " "))+"/\\  "+action+"\r\n");
	}


}