In my opinion you could rewrite your mousePressed like this:
function mousePressed() {
if (state==0) {
mousePressedForState0();
}
//----
else if (state==1) {
mousePressedForState1();
}
//----
else if (state==2) {
mousePressedForState2();
}
//----
else if (state==3) {
mousePressedForState3();
}
//----
else if (state==4) {
mousePressedForState4();
}
//----
else if (state==5) {
mousePressedForState5();
} else {
// error
println ("Error");
exit();
return;
}//else
//
}//function
Then make those functions and put what you have in mousePressed now inside those functions (the stuff for state 0 in the appropriate function mousePressedForState0() and so on).
Then your code is better readable since it’s in nice modules.
Same goes for function draw() by the way