Exception in thread "main" java.lang.NumberFormatException:For input String

Question

this is a code about arrylist. but when I debug it.it metion:Exception in thread "main" java.lang.NumberFormatException:For input String at java.lang.NumberFormatException.forInputString(numberFomatExceptionio java:48)
at java.lang.Integer.parseInt(integer.java:468)
at java.lang.Integer.parseInt(integer.java:497)
at Get.getInt(manerger.java:208)
at LinkList.insertFirst(manager.java:94)
at manager.main(manager.java;20)
this is my code:
import java.io.*;
import java.lang.*;
public class manager
     public static void main(String args[]) throws IOException
     LinkList list=new LinkList();
     System.out.println("input S can scan the grade\ninput D can delete one entry\ninput U can update the entry\ninput A can add one entry\ninput E can end");
     int cr=System.in.read();
switch(cr)
     case 'A':
     list.insertFirst();break;//this is 20 row
     case 'S':
     System.out.println("input the s");break;
     case 'D':
     System.out.println("input the d");break;
     case 'U':
     System.out.println("input the u");break;
class Link
public int number;
public String name=new String();
public int chs;
public int eng;
public int math;
public Link next;
public Link(int number,String name, int chs,int eng,int math)
this.number=number;
this.name=name;
this.chs=chs;
this.eng=eng;
this.math=math;
public Link()
     this(0,"",0,0,0);
public void displayLink()
System.out.println(number + " "+name+ " "+chs+ " "+eng+ " "+math+ " ");
class LinkList
public Link first;
public LinkList()
first = null;
public boolean isEmpty()
return first==null;
public void displayList()
     System.out.println("");
     Link current=first;
     while(current!=null)
          current.displayLink();
          current=current.next;
     System.out.println("");
public Link insertFirst() throws IOException
     Get getdata=new Get();
     int number=getdata.getInt();//this is 94 row
     String name=getdata.getString();
     int chs=getdata.getInt();
     int eng=getdata.getInt();
     int math=getdata.getInt();
     Link newLink = new Link(number,name,chs,eng,math);
     first=newLink;
     return first;
public Link find(int key)
     Link current=first;
     while(current.number!=key)
          if(current.next==null)
          return null;
          else
          current=current.next;
     return current;
public Link update(int key) throws IOException
     Link current=first;
     while(current.number!=key)
     if(current.next==null)
     return null;
     else
          System.out.println("Input the first letter of the subject:");
     int c=System.in.read();
     Get get=new Get();
          switch(c)
               case 'c':
               current.chs=get.getInt();break;
               case 'e':
               current.eng=get.getInt();break;
               case 'm':
               current.math=get.getInt();break;
     return current;
public float average(char key)
     Link current=first;
     float total=0;
     float average=0;
     float counter=0;
     if(current==null)
     return 0;
     while(current!=null)
          switch(key)
               case 'c':
               total=current.chs+current.next.chs;break;
               case 'e':
               total=current.eng+current.next.eng;break;
               case 'm':
               total=current.math+current.next.math;break;
          current=current.next.next;
          counter++;
     average=total/counter;
     return average;
public Link delete(int key)
     Link current=first;
     Link previous=first;
     while(current.number!=key)
          if(current.next==null)
          return null;
          else
               previous=current;
               current=current.next;
          if(current==first)
          first=first.next;
          else
          previous.next=current.next;
          return current;
class Get
public static String getString() throws IOException
System.out.println("Input your name:");
InputStreamReader str = new InputStreamReader(System.in);
BufferedReader br = new BufferedReader(str);
String s = br.readLine();
return s;
public static int getInt() throws IOException
System.out.println("Input your data:");
String st = getString();
return Integer.parseInt(st);//this is 208 row
}

Answer 1

It may be that the code in getString() returns a
String that ends with a newline. If that is the
problem, you can use
return (Integer.parseInt(st)).trim();1. getString will never return a String ending in newline. BufferedReader.readLine strips off the newline.
2. Even if you had a newline, String.trim doesn't trim newlines.
3. You would need to trim the String, not the int:
return (Integer.parseInt(st.trim()));As JimDinosaur said, you are passing bad data (the value of "st").
In getInt, add this before trying to parse "st":
System.out.println("###"+st+"###");What does it print?