java - How to use variables defined in an if statement outside of it -

i have been trying make calculator , when define variables inside if statement says:

exception in thread "main" java.lang.error: unresolved compilation problem: blocknum cannot resolved variable @ firsttry.main.main(main.java:57)

now know have define variables outside of if statements, because of variable scope, when try so:

package firsttry;  import java.util.scanner;  public class main {     public static void main(string args[]){         int blocknum;         blocknum = 1; 

i error of:

exception in thread "main" java.lang.error: unresolved compilation problem: duplicate local variable blocknum
@ firsttry.main.main(main.java:36)

so how fix problem? have read solution problem variable scope define variable outside of if statement, doesnt seem work me?

my full code:

package firsttry;  import java.util.scanner;  public class main {     public static void main(string args[]) {         int blocknum;         blocknum = 1;         csv bgather = new csv();         toolname atool = new toolname();         scanner input = new scanner(system.in);         //welcoming message         system.out.println("welcome minecraft build/excavate calculator"             + "\nits suggested use tools suitable block"             + "\nthat breaking faster"             + "");          //gatheres user variables         system.out.println("what block gathering? (use minecraft block ids)");         string block = input.next();          system.out.println("what tool using , 1 using hand , 4 diamond");         int tool = input.nextint();         system.out.println("do want enter dimensions of area excavating"             + "or exact block number"             + "1 dimensions "             + "2 exact number");         int typeofselection = input.nextint();         if (typeofselection == 1) {             system.out.println("height of area");             int height = input.nextint();             system.out.println("length of area");             int length = input.nextint();             system.out.println("width of area");             int width = input.nextint();         } else if (typeofselection == 2) {             system.out.println("exact amount of blocks");             int blocknum = input.nextint();         } else {             system.out.println("errorrrr");         }          //csv file stuf         string toolname = atool.nameoftool(tool);         string blockname = bgather.name(block);          double blockbreak = bgather.speed(tool,block);         input.close();          //overall calculations         if (typeofselection == 2) {             system.out.println(blocknum);         }          system.out.println("you gatherering " + blockname + " using " +       toolname + " \nand take " + blockbreak + " seconds per block");     } } 

else if (typeofselection == 2){         system.out.println("exact amount of blocks");         int blocknum = input.nextint(); } 

if int blocknum same variable variable declared @ top, remove int part.

else if (typeofselection == 2){     system.out.println("exact amount of blocks");     blocknum = input.nextint(); }