(java) can anyone me with this question

Your print function is too specific. It should be more like:

for( int i = 0; i < data.length; i++ )
    System.out.print( data[ i ] );

append() would be something like:

int[] c = new int[ a.length + b.length ];
int j = 0;
for( int i = 0; i < a.length; i++ )
    c[ i ] = a[ i ];

for( int i = j; i < ( b.length + a.length ); i++ )
    c[ i ] = b[ i ];
return( c );