What design pattern is the following class an example of$?$

public class X implements Y $\{$

private ArrayList members;

@Override

public boolean foo$()\{$

boolean v $=$ true;

for $($Y member: members$)\{$

v $=$ v && member.foo$()$;

$\}$

return v;

$\}$

void addY$($Y y$)\{$

members.add$($y$)$;

$\}$

$\}$

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