How to convert a string to an integer without using javaapi

Reference: http://blog.csdn.net/greatmind829/article/details/7870719

 

public class Convert { 
 
    public static void main(String[] args) { 
       Convert convert = new Convert(); 
        int return_num = convert.convert_num("12345"); 
        System.out.println("retunr nam --"+return_num) ; 
        
    } 
     
    /**
     * Convert a string of numbers to numbers
     */ 
     
   public int convert_num (String val){ 
         
        int return_val = 0 ; 
       char[] char_arr = val.toCharArray(); 
    
       for (int i = 0; i < char_arr.length; i++) { 
           char c = char_arr[i]; 
            //Example: 100 = 10 *10   
            int val_v = (int)Math.pow(10, char_arr.length-(i+1));  
            //in During operation, char is automatically converted to int type for calculation
            return_val =  return_val + (c-48) *val_v; 
       } 
      return return_val; 
        } 
}