LeetCode----8. String to Integer (atoi)(Java)

 package myAtoi8;
 /*
  * Implement atoi to convert a string to an integer.
 Hint: Carefully consider all possible input cases. If you want a challenge, please do not see below and ask yourself what are the possible input cases.
 Notes: It is intended for this problem to be specified vaguely (ie, no given input specs). You are responsible to gather all the input requirements up front.
 Update (2015-02-10):
 The signature of the C++ function had been updated. If you still see your function signature accepts a const char * argument, please click the reload button  to reset your code definition.
 */

 public class Solution {
     public static int myAtoi(String str) {
         StringBuilder sb=new StringBuilder();
         int flag=0;
         if(str.length()==0)
             return 0;
         else{
             for(int i=0;i<str.length();i++){
                 if(str.charAt(i)<'0'||str.charAt(i)>'9')
                     if(str.charAt(i)=='0'||str.charAt(i)==' ')
                         if (sb.length()==0)
                             continue;
                         else
                             break;
                     else if (str.charAt(i)=='-')
                         if (flag==0){
                             flag=-1;
                             sb.append('0');
                         }
                         else
                             break;
                     else if (str.charAt(i)=='+')
                         if (flag==0){
                             flag=1;
                             sb.append('0');
                         }
                         else
                             break;
                     else
                         break;
                 else
                     sb.append(str.charAt(i));
                 }
         }
         if(sb.length()==0)
             return 0;
         else if(sb.length()>12)
             str=sb.substring(sb.length()-12);
         else
             str=sb.toString();
         if (flag==-1)
             str="-"+str;
         long result=Long.parseLong(str);
         System.out.println(result);
         if (result>2147483647)
             return 2147483647;
         else if (result<-2147483648)
             return -2147483648;
         else
             return (int)result;

     }
     public static void main(String[] args){
         String str1="";//
         String str2="+";//
         String str3="              +45555";//
         String str4="              -45555";//-45555
         String str5="2147483647";//
         String str6="2147483648";//
         String str7="+-2";//
         String str8="-+2";//
         String str9="++2";//
         String str10="-2147483648";//-2147483648
         String str11="   - 321";//
         String str12="      -11919730356x";//-2147483648
         String str13="1234567890123456789012345678901234567890";//
         System.out.println(myAtoi(str1));
         System.out.println(myAtoi(str2));
         System.out.println(myAtoi(str3));
         System.out.println(myAtoi(str4));
         System.out.println(myAtoi(str5));
         System.out.println(myAtoi(str6));
         System.out.println(myAtoi(str7));
         System.out.println(myAtoi(str8));
         System.out.println(myAtoi(str9));
         System.out.println(myAtoi(str10));
         System.out.println(myAtoi(str11));
         System.out.println(myAtoi(str12));
         System.out.println(myAtoi(str13));

     }
 }