New rules means we cannot hand out answers for assignments, which this seems to indicate considering your refusal to use concat.
I’m pointing you to the video for this precise reason, the problem here is not too difficult providing that you think about the steps.
ie
//step 1------------------------- create new array
float[] array = new float[a.length.b.length];
//step 2------------------------- Read from array a
for(int i=0;i<a.length;i++){
?????
}
//step 2------------------------- Read from array b
for(int i=0;i<b.length;i++){
?????
}
// step 4-----------------------------????
this is really the entirety of the code, but I cannot help more than this.