Java palindrome tester

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Java

import java.util.*;
 
class Palindrome
{
  public static void main(String args[])
  {
    String inputString;
    Scanner in = new Scanner(System.in);
 
    System.out.println("Input a string");
    inputString = in.nextLine();
 
    int length  = inputString.length();
    int i, begin, end, middle;
 
    begin  = 0;
    end    = length - 1;
    middle = (begin + end)/2;
 
    for (i = begin; i <= middle; i++) {
      if (inputString.charAt(begin) == inputString.charAt(end)) {
        begin++;
        end--;
      }
      else {
        break;
      }
    }
    if (i == middle + 1) //when or how i will be middle +1 if i<=middle
{
      System.out.println("Palindrome");
    }
    else {
      System.out.println("Not a palindrome");
    } 	
  }
}

What I have tried:

above code works. i found this code on internet it is not the code i wrote. but i am confused when i is equal to middle+1. for loop condition is i<=middle. please explain to me.

Posted 10-Nov-17 18:11pm

Member 13515057

Updated 10-Nov-17 18:53pm

Patrice T

v2

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Patrice T · Answer 1 · 2017-11-10T18:20:00

Quote:
but i am confused when i is equal to middle+1. for loop condition is i<=middle. please explain to me.

Use the debugger and see by yourself how this code works!

There is a tool that allow you to see what your code is doing, its name is debugger. It is also a great learning tool because it show you reality and you can see which expectation match reality.
When you don't understand what your code is doing or why it does what it does, the answer is debugger.
Use the debugger to see what your code is doing. Just set a breakpoint and see your code performing, the debugger allow you to execute lines 1 by 1 and to inspect variables as it execute.

Debugger - Wikipedia, the free encyclopedia[^]
http://docs.oracle.com/javase/7/docs/technotes/tools/windows/jdb.html[^]
https://www.jetbrains.com/idea/help/debugging-your-first-java-application.html[^]
The debugger is here to show you what your code is doing and your task is to compare with what it should do.
There is no magic in the debugger, it don't find bugs, it just help you to. When the code don't do what is expected, you are close to a bug.

Peter_in_2780 · Answer 2 · 2017-11-10T18:22:00

Solution 2

Your loop increments i by 1. When it is no longer <= middle (i.e. has been incremented to middle+1) then control "falls out" of the loop. Any basic textbook will explain how a for loop works.

Posted 10-Nov-17 18:22pm

Peter_in_2780