อาจจะมองเยอะ แต่เป็น Algorithms ง่ายๆ ช่วยดูทีครับ
import javax.swing.*;
class All
{
public static void main(String[] args)
{
All see = new All();
String s1,s2,str="",s3;
int a,b,p,d;
s2=JOptionPane.showInputDialog("Set Row Array ");
if(s2==null)
{
a=7;
str="User Cancel Or Not set value set array is 7";
JOptionPane.showMessageDialog(null,str,"Message",JOptionPane.INFORMATION_MESSAGE);


}
else if(s2.equals(""))
{
a=7;
str="User Cancel Or Not ser value set array is 7";
JOptionPane.showMessageDialog(null,str,"Message",JOptionPane.INFORMATION_MESSAGE);

}
else if(true){
try
{
Integer.parseInt(s2);
b=Integer.parseInt(s2);
if(b>30)
{
a=5;
str="User Cancel Or Not ser value set array is 5";
JOptionPane.showMessageDialog(null,str,"Message",JOptionPane.INFORMATION_MESSAGE);

}
else{
if (b<2)
{
a=5;
str="Number Is not Prime is set 5 array";
JOptionPane.showMessageDialog(null,str,"Message",JOptionPane.INFORMATION_MESSAGE);

}
else if(b==2)
{
a=2;
JOptionPane.showMessageDialog(null,str,"Message",JOptionPane.INFORMATION_MESSAGE);

}
else if(b>2)
{
p=Prime(b);
a=p;
}
}
}

catch(NumberFormatException e)
{
a=7;
str="Not number is 7";
JOptionPane.showMessageDialog(null,str,"Message",JOptionPane.INFORMATION_MESSAGE);
}
System.out.println("array"+a);//ตั้งแต่บรรทัดนี้เหมือนมันไม่รู้จักตัวแปร a ไม่รู้เพราะอะไร }
int data[] = new int[a] ;//ทำให้ผมใส่ a เป็น array ไม่ได้
do{

d=Integer.parseInt(JOptionPane.showInputDialog("----------Main Menu----------\n =============================== \n 1.Set Value \n 2.Show Value \n 3.Summation Data\n 4.Show data \n 5.Exit"));
if(d==1)
setValue(data);

}while(d!=5);
}

public static int Prime(int c)
{
int r,temp;
for(int i=3,end = (int)Math.sqrt(c);i<=end;i+=2){
if (c % i == 0) {
r=5;
temp=r;
c=temp;
}
else {
r=c;
temp=r;
c=temp;
}
}
return c;
}
public static void setValue(int slot[])
{
for(int i=0;i<slot.length;i++)
{
slot[i]=1+(int)(Math.random()*12);
}
String str="create Array finish";
JOptionPane.showMessageDialog(null,str,"Message",JOptionPane.INFORMATION_MESSAGE);
}
}

ทำไงดีครับ มันไม่รู้จักตัวแปร a

จากคุณ กบน้อย (A:125.25.73.150 X:)