// innerclasses/Sequence.java

// (c)2021 MindView LLC: see Copyright.txt

// We make no guarantees that this code is fit for any purpose.

// Visit http://OnJava8.com for more book information.

// Holds a sequence of Objects

interface Selector {

boolean end();

Object current();

void next();

}

public class Sequence {

private Object[] items;

private int next = 0;

public Sequence(int size) {

items = new Object[size];

}

public static void main(String[] args) {

Sequence sequence = new Sequence(10);

for (int i = 0; i < 10; i++)

sequence.add(Integer.toString(i));

Selector selector = sequence.selector();

while (!selector.end()) {

System.out.print(selector.current() + " ");

selector.next();

}

}

public void add(Object x) {

if (next < items.length)

items[next++] = x;

}

public Selector selector() {

return new SequenceSelector();

}

private class SequenceSelector implements Selector {

private int i = 0;

@Override

public boolean end() {

return i == items.length;

}

@Override

public Object current() {

return items[i];

}

@Override

public void next() {

if (i < items.length) i++;

}

}

}

/* Output:

0 1 2 3 4 5 6 7 8 9

*/