This code won't compile:

int[] num = new int[ 5 ];
num[ 0 ] = 3;

void hello( )
{
println("HI");
}

I get an unexpected token: void. It always happens when i use any kind of
dynamic allocation. Changing the order like this:

void hello( )
{
println("HI");
}

int[] num = new int[ 5 ];
num[ 0 ] = 3;

I get an "Expecting RBRACK, found '0'" error. The allocation works fine if
specified inside a function block, but not in the global environment.

that's just a bug in your code. except for in special cases, you cannot
assign the contents of arrays outside of methods.

int[] num = new int[ 5 ];
num[ 0 ] = 3; // this line is just bad syntax

void hello( )
{
println("HI");
}

to fix this, use:

int[] num = new int[ 5 ];

void hello( )
{
num[ 0 ] = 3; // it's ok to do this here
println("HI");
}