Integer.parseInt(String)

[Bindu Lakhanpal]

This is my own practice code.
But i could not understand why i get this output.Why there is NumberFormatException in line1

package exc;
 import java.io.*;
import java.util.*;
 class newException extends Exception{
                                                          }
public class Test{
                  
public static void main(String str[])
        {    char [] n=new char[3]; 
              int k=0;
              String p=null;
               System.out.println("Enter age");
                  try{
                      BufferedReader stdin=new BufferedReader(new InputStreamReader(System.in));
                      stdin.read(n);
                       for(int i=0;i<n.length;i++)
                                           {
                                                if(p==null)
                                                          {
                                                           p=Character.toString(n[i]);
                                                            }
                                                else
                                                            {
                                                       p=p.concat(Character.toString(n[i]));
                                                             }
                                             }
                     System.out.println(p);
                     k=Integer.parseInt(p);              // line 1
                  }
                  catch(IOException ss)
                           {
                              System.out.println("IOException is thrown");
                              }
                      try
                           {
                            Age ag= new Age(k);
                           ag.func1();
                             }
                    catch(newException e)
                              {
                                System.out.println("Error");
                                }
 
               }
         }
           class Age{
                  int age;
                  Age(int a)
                   {
                  age=a;
                   }
              public  void func1() throws newException {
              if(age>100||age<1)
                     throw new newException();
                                                                     }
                 }

output:
Enter age
23
23
Exception in thread "main" java.lang.NumberFormatException: For input string: "2
"
at java.lang.NumberFormatException.forInputString(NumberFormatException.
java:48)
at java.lang.Integer.parseInt(Integer.java:456)
at java.lang.Integer.parseInt(Integer.java:497)
at exc.Test.main(Test.java:28)

[Balu Sadhasivam]

  
#                       BufferedReader stdin=new BufferedReader(new InputStreamReader(System.in));  
#                       stdin.read(n);  
#                        for(int i=0;i<n.length;i++)  
#                                            {  
#                                                 if(p==null)  
#                                                           {  
#                                                            p=Character.toString(n[i]);  
#                                                             }  
#                                                 else  
#                                                             {  
#                                                        p=p.concat(Character.toString(n[i]));  
#                                                              }  
#                                              }  
#                      System.out.println(p);  
#                      k=Integer.parseInt(p);              // line 1    

This all sounds problem inviting. You got readLine() method in BufferedReader which directly returns your String.
check readLine()>

[Bindu Lakhanpal]

Thanks,readLine() worked very well.
But i was just testing read() method in this program.
String p is printing alright.Then what could be the problem parsing it to int.

[Balu Sadhasivam]

String p is printing alright.Then what could be the problem parsing it to int.

Add SOPs inside the loop and see what each character it prints. char[] array is of size 3 , check out what is n.length() and check for any special characters in the final String ( space may be misleading when you print like that )

[Bindu Lakhanpal]

Yes, you are right. The space in end is the problem.
I changed the code as suggested by you.
See the outputs.

package exc;
 import java.io.*;
import java.util.*;
 class newException extends Exception{
                                                          }
public class Test{
                  
public static void main(String str[])
        {    char [] n=new char[3]; 
              int k=0;
              String p=null;
               System.out.println("Enter age");
                  try{
                      BufferedReader stdin=new BufferedReader(new InputStreamReader(System.in));
                 stdin.read(n);
                       for(int i=0;i<n.length;i++)
                                           {
                                                if(p==null)
                                                          {
                                                           p=Character.toString(n[i]);
                                                            }
                                                else
                                                            {
                                                       p=p.concat(Character.toString(n[i]));
                                                             }
                                             }
                     System.out.println(p);
                     for(int l=0;l<p.length();l++)
                               {
                                System.out.println(p.charAt(l));
                                } 
                     k=Integer.parseInt(p);              // line 1
                  }
                  catch(IOException ss)
                           {
                              System.out.println("IOException is thrown");
                              }
                      try
                           {
                            Age ag= new Age(k);
                           ag.func1();
                             }
                    catch(newException e)
                              {
                                System.out.println("Error");
                                }
 
               }
         }
           class Age{
                  int age;
                  Age(int a)
                   {
                  age=a;
                   }
              public  void func1() throws newException {
              if(age>100||age<1)
                     throw new newException();
                                                                     }
                 }

outputs:C:\IOEX\classes>java exc.Test
Enter age
456
456
4
5
6
Error

C:\IOEX\classes>java exc.Test
Enter age
56
56
5
6

Exception in thread "main" java.lang.NumberFormatException: For input string: "5
"
at java.lang.NumberFormatException.forInputString(NumberFormatException.
java:48)
at java.lang.Integer.parseInt(Integer.java:456)
at java.lang.Integer.parseInt(Integer.java:497)
at exc.Test.main(Test.java:32)

So,using trim() made the code run.

k=Integer.parseInt(p.trim());      

[Balu Sadhasivam]

Oh great . I like the way people work out their own code and find issues just by guiding them.

[Bindu Lakhanpal]

yes,thank you so much.
I am out of touch from core concepts for almost 2 months.
And i have forgotten so much. .
Now i understand why Arulk always says" keep applying what you have learnt in the certification result forum.
I hope ranchers here will help me just like you did.
Thanks again.