Method equals

chapter19/src/main/java/com/seaofnodes/simple/Ary.java:200–209

( Object o )

    // underlying array.  If the hashCode() is used (e.g., inserting into a
    // HashMap) and the then the array changes, the hashCode() will change also.
    @Override public boolean equals( Object o ) {
        if( this==o ) return true;
        if( !(o instanceof Ary ary) ) return false;
        if( _len != ary._len ) return false;
        if( _es == ary._es ) return true;
        for( int i=0; i<_len; i++ )
            if( !(_es[i]==null ? (ary._es[i] == null) : _es[i].equals(ary._es[i])) )
                return false;
        return true;
    }
    @Override public int hashCode( ) {
        int sum=_len;
        for( int i=0; i<_len; i++ )