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How to do repeated sequence check

Question: Repeated Sequence Check
The program should enter a string (possibly containing blanks), and determine whether the characters are in
lexicographic order.
For example:
“12AABab” is in order since each character is less than or equal to the one following it (‘1’ < ‘2’, ‘2’ <
‘A’, ‘B’ < ‘a’, etc.) according to the Unicode character sequence.
“abCDef” is out of order, because ‘b’ > ‘C’ (lower-case letters come after upper-case letters in the
Unicode sequence).
If the string is in order, the program should display “The input is in order”; otherwise, it should display
“The input is out of order”
The program should repeat this process until the user enters the string “quit”, regardless of case. It should
not check the sequence of “quit”.
Finally, the program should display “Goodbye”.
Notes:
This program will require nested loops. The inner loop will check the sequence of the input, while
the outer loop will repeat the input and check process.
Be sure to reinitialize all variables at the start of the outer loop.
A string of length 0 or 1 is considered to be in order by definition.
what I could do best is: (I tried with 2 other different methods I could send it too if you like)
package homelab03;
import java.util.Scanner;
public class Quest3deneme3 {
public static void main(String[] args) {
// TODO Auto-generated method stub
String whole,remain,d,e;
char h1,h2;
int lenght,b,c,sayac;
//int[] a;
String[] a;
Scanner keyboard = new Scanner(System.in);
System.out.println("Enter an input string:");
whole = keyboard.nextLine();
whole=whole.replaceAll("\\s+","");
lenght=(int)whole.length();
//System.out.println(+lenght);
remain=whole;
sayac=0;
c=0;
b=0;
a= new String[lenght];
//boolean cem = d.compareTo(e);
while(b<lenght)
{
a[b]=remain.substring(b,b+1);
remain=remain.substring(b+1);
System.out.println(a[b]);
d=a[b];
e=a[c];
while(a[b]<a[c] )
{
sayac=sayac+1;
h1=h2;
}
}
if(sayac==lenght)
{
System.out.println("oley");
}
else
{
System.out.println("nooo");
}
}
//a[b]=remain.substring(b,b+1);
//remain=whole.substring(b+1);
//System.out.println(a[b]);
}
note we haven't learned a[b] <= this thing yet but I find it online if the solution won't require that that would be better.
note 2: we haven't learned regex either I think that might be dissalowed (I found some answers with that online but I think I won't get credit for that)

You could check this code. Maybe it will inspire you :)
import java.util.Scanner;
public class howToDoRepeatedSequanceCheck {
public void repeatedTests() {
String whole;
int inputLength,i;
Scanner keyboard = new Scanner(System.in);
System.out.println("Enter an input string:");
whole = keyboard.nextLine();
while(!whole.equals("quit")) {
whole=whole.replaceAll("\\s+","");
inputLength = whole.length();
boolean isInOrder = true;
i = 0;
while(isInOrder && i<inputLength-1 ) {
if(whole.charAt(i)<whole.charAt(i+1)) {
// System.out.println("ok " + whole.charAt(i)+ " < " +whole.charAt(i+1));
}else {
// System.out.println("error");
isInOrder = false;
}
i++;
}
if(isInOrder == true) {
System.out.println("The input is in order");
}else {
System.out.println("The input is out of order");
}
System.out.println();
System.out.println("Enter an input string:");
whole = keyboard.nextLine();
}
System.out.println("Goodbye");
}
}

String matching program

I am trying to make a java program to reverse the given string and each time iterate, compare with the reversed string then to print pass if matched else fail.
My program is:
package sss;
import java.util.Scanner;
public class ssi {
/**
* #param args
*/
public static void main(String[] args) {
String original,reverse="";
Scanner sc=new Scanner(System.in);
int ascii11,ascii12,ascii13,ascii14;
System.out.println("enter the string to be reversed");
original=sc.next();
int length=original.length();
for(int i=length-1;i>=0;i--)
{
reverse=reverse+original.charAt(i);
}
System.out.println(reverse);
//System.out.println(original);
for(int j=0;j<original.length()-1;j++)
{
ascii11=original.charAt(j);
ascii12=original.charAt(j+1);
ascii13=reverse.charAt(j);
ascii14=reverse.charAt(j+1);
if(Math.abs(ascii11-ascii12) == Math.abs(ascii13-ascii14))
{
System.out.println("pass");
}
else
{
System.out.println("fail");
}
}
// TODO Auto-generated method stub
sc.close();
}
}
here each time when the for loop iterates i am getting pass or fail for each pair of numbers but i want the o/p as to print only pass or fail ONCE.
can any one help me out please...

Example Code:
import java.util.Scanner;
public class PalindromeChecker {
public static void main(String[] args) {
String original;
Scanner sc = new Scanner(System.in);
System.out.print("Enter the string to be reversed: ");
original = sc.next();
int halfLength = original.length()/2;
int lastIndex = original.length() - 1;
int i;
for(i = 0; i < halfLength; i++) {
if(original.charAt(i) != original.charAt(lastIndex - i)) {
System.out.println("Fail!");
break;
}
}
// Managed to match all characters
if(i == halfLength) {
System.out.println("Pass!");
}
sc.close();
}
}
Input/Output:
Enter the string to be reversed: banana
Fail!
Enter the string to be reversed: RADAR
Pass!
Enter the string to be reversed: asdwwdsa
Pass!
So the idea is to:
Compare the first half of the string with the second half of the string
Compare the first character with the last character
Compare the 2nd character with the 2nd last character, and so on.
If any character does not match, print Fail!
If the loop finishes, it implies that the string is a palindrome (original == reversed), print Pass!

You need to flag each comparison of the original and reversed characters with either a pass or a fail boolean value. Obviously if any of them are flagged with a fail, you can then terminate the algorithm and print fail. If the for loop continues with a pass right to the end, then print pass once outside of the for loop.

Your print statement is inside the loop , so its printing "pass" or "fail" for each loop. You should use a flag to check whether all the ascii characters are same. and then check the status of flag outside the loop.
OR
Use StringBuffer it has a built-in method to reverse string.
StringBuffer input = new StringBuffer("Your String to reverse");
String reverse = input.reverse().toString();
if(input.equals(reverse))
System.out.println("pass");
else
System.out.println("fail");

Move your if condition out of for loop.
for(int j=0;j<original.length()-1;j++)
{
ascii11=original.charAt(j);
ascii12=original.charAt(j+1);
ascii13=reverse.charAt(j);
ascii14=reverse.charAt(j+1);
}
if(Math.abs(ascii11-ascii12) == Math.abs(ascii13-ascii14))
{
System.out.println("pass");
}
else
{
System.out.println("fail");
}

How do you check if a string is a palindrome in java?

I am trying to write a program that checks if a string is a palindrome and so far I know I am on the right path but when I enter my code it keeps on running for ever. I don't know what the problem is and would like help finding out the solution. In my program I want the user to enter word or words in the method Printpalindrome and then the program should know if the string is a palindrome or not.
Here is my code:
...
Scanner console = new Scanner (System.in);
String str = console.next();
Printpalindrome(console, str);
}
public static void Printpalindrome(Scanner console, String str) {
Scanner in = new Scanner(System.in);
String original, reverse = "";
str = in.nextLine();
int length = str.length();
for ( int i = length - 1; i >= 0; i-- ) {
reverse = reverse + str.charAt(i);
}
if (str.equals(reverse))
System.out.println("Entered string is a palindrome.");
}
}

Because of this line:
n = in.nextLine();
your program is waiting for a second input, but you already got one before entering the function.
Remove this line and it works.
Here's your program, cleaned (and tested) :
public static void main(String[] args){
Scanner console = new Scanner (System.in);
String n = console.next();
Printpalindrome(n);
}
public static void Printpalindrome(String n){
String reverse = "";
for ( int i = n.length() - 1; i >= 0; i-- ) {
reverse = reverse + n.charAt(i);
System.out.println("re:"+reverse);
}
if (n.equals(reverse))
System.out.println("Entered string is a palindrome.");
else
System.out.println("Entered string is NOT a palindrome.");
}
Of course, this isn't the best algorithm, but you already know there are many QA on SO with faster solutions (hint: don't build a string, just compare chars).

Remove
Scanner in = new Scanner(System.in);
and
n = in.nextLine();
from Printpalindrome function
and it should work.

This can be implemented in a far more efficient manner:
boolean isPalindrom(String s){
if (s == null /* || s.length == 0 ?*/) {
return false;
}
int i = 0, j = s.length() - 1;
while(i < j) {
if(s.charAt(i++) != s.charAt(j--)) {
return false;
}
}
return true;
}
The argument for PrintPalindrom is ignored. You read another value with `in.nextLine()'. Which is the reason for your issues.

Ur code with some correction:-
import java.util.*;
class Palindrome
{
public static void main(String args[])
{
String original, reverse = "";
Scanner in = new Scanner(System.in);
System.out.println("Enter a string to check if it is a palindrome");
original = in.nextLine();
int length = original.length();
for ( int i = length - 1; i >= 0; i-- )
reverse = reverse + original.charAt(i);
if (original.equals(reverse))
System.out.println("Entered string is a palindrome.");
else
System.out.println("Entered string is not a palindrome.");
}
}

I tried your code and what i observed was that :
first of all you are making a string to enter on the line 2 of your code:
String n=console.next();
next the the program again goes to waiting when this line gets executed:
n = in.nextLine();
actually this particular line is also expecting an input so that is why the program halt at this point of time.
If you enter your String to be checked for palindrome at this point of time you would get the desired result .
But I would rather prefer you to delete the line
n = in.nextLine();
because, with this, you would have to enter two words which are ambiguous.

Issue with Palindrome class using Stacks

I am trying to write a Palindrome class using Stacks to determine if a word entered by user is a palindrome. There seems to be an issue in my Palindrome class. Can someone please help me identify it? My program works but no matter what word I type, it returns that the word is not a palindrome.
import java.util.Stack;
public class Palindrome
{
public Palindrome()
{
Stack stack = new Stack();
String input = "";
boolean isPalindrome = false;
for(int i = 0; i < input.length(); i++)
{
stack.push(i);
}
String opposite = " ";
while(!stack.isEmpty())
{
opposite = opposite + stack.pop();
}
if(input.equals(opposite))
isPalindrome = true;
else
isPalindrome = false;
}//end main
}//end class Palindrome
Here is my PalindromeCheck class:
import java.util.Scanner;
public class PalinDromeCheck
{
public static void main(String[] args)
{
Palindrome pal = new Palindrome();
Scanner type = new Scanner(System.in); //create scanner for user to type a word
String word = null; //initial word to check
String stop = null; //stops processing of word
do
{
System.out.println("Enter a word to determine if it is a palindrome: ");
word = type.nextLine(); //user types word
if(pal.equals(word))
System.out.println("is a palindrome");
else
System.out.println("is not a palindrome\n");
System.out.println("Would you like to try another word? Type Y for 'Yes' or N for 'No'");
stop = type.nextLine(); //stops processing
}
while(stop.equalsIgnoreCase("y")); //continues to process and ignores upper or lowercase Y
}
}

You have several bugs.
First, you need to give the input to the Palindrome class.
Second, when you reverse the input using stack, you push the index on the stack, not the character.
Third, it's not a good practice to do everything une constructor. Palindrome class doesn't need to know the input as member or for initialization purpose
If you don't need to have several implementation of Palindrome, you shall use a static method.
Try this :
public class Palindrome
{
public static boolean isPalindrome(String input)
{
char[] inputArray = input.toCharArray();
bool isOk = true;
for(int i = 0; i < inputArray.length/2 && isOk; i++){
isOk &= inputArray[i] == inputArray[inputArray.length - i - 1];
}
return isOk;
} // end method
} //end class Palindrome
Then, your main function could be :
public static void main(String[] args)
{
System.out.println("Enter a word to determine if it is a palindrome: ");
word = type.nextLine(); //user types word
if(Palindrome.isPalindrome(word)) {
System.out.println("is a palindrome");
} else {
System.out.println("is not a palindrome\n");
}
} // End of main

Is this your full Palindrome-Class? If yes, it has no input to handle!
public class Palindrome
{
public static boolean isPalindrome(String input)
{
Stack stack = new Stack();
for(int i = 0; i < input.length(); i++)
{
stack.push(input.charAt(i));
}
String opposite = "";
while(!stack.isEmpty())
{
opposite = opposite + stack.pop();
}
return input.equals(opposite);
}//end main
}//end class Palindrome
this creates a static method you can use in your code like:
System.out.println("Enter a word to determine if it is a palindrome: ");
word = type.nextLine(); //user types word
if(Palindrome.isPalindrome(word))
System.out.println("is a palindrome");
else
System.out.println("is not a palindrome\n");

Your input is empty because you set input to "" in the constructor. You would be better off using a constructor argument to contain the input and then keep track of that using a member variable.
The code you typed is probably better suited to be in a method (equals perhaps? You will have to override this). You might want to consider pushing the character from the input string onto the stack rather then 0, 1, 2, 3... n (where n = input.length() - 1).
Your current .equals(word) does not do what you think it does because you have not provided an overload.

2D Arrays in Java Program

My program is supposed to gets a phrase from the user then returns to the user an encrypted code of their choice (either ROT13 or ATBASH) of the phrase they entered. My code compiles and everything and lets the user input the required stuff but when they enter the phrase to be encrypted, nothing happens.. like the new encrypted code doesnt show up, and i dont know what wrong with it!
Please help! Thank you!
import java.io.*;
public class J4_1_EncryptionVer4
{
public static void main (String [] args) throws IOException
{
BufferedReader myInput = new BufferedReader (new InputStreamReader (System.in));//BufferedReader reads user input
//String array letterA[] is initialized
String [][] letterA = new String [][]{
{"A","B","C","D","E","F","G","H","I","J","K","L","M","N","O","P","Q","R","S","T","U","V","W","X","Y","Z"},
{"N","O","P","Q","R","S","T","U","V","W","X","Y","Z","A","B","C","D","E","F","G","H","I","J","K","L","M"},
{"Z","Y","X","W","V","U","T","S","R","Q","P","O","N","M","L","K","J","I","H","G","F","E","D","C","B","A"},
};
System.out.println ("Enter '1' for ROT13 or '2' for ATBASH");//asks user to choose method
String numA = myInput.readLine();//reads user input and assigns it to string
int num = Integer.parseInt (numA);//converts string to integer
int a = 0;//int a is declared
if (num == 1){//if user enters 1
a = 1;//set a to 1
}
if (num == 2) {//end if//if user enters 2
a = 2;//set a to 2
}//end if
System.out.println ( a);
System.out.println(num);
System.out.println ("Please enter a phrase: ");//asks user to enter phrase
String message = myInput.readLine();//reads user input and assigns it to string
int x = 0; //declares int var x
System.out.println ("Your Encrypted code is: ");//prints out scentence
while (x < message.length())//while loop will run while x is less that the phrase length
{
String text = message.toUpperCase();//converts user input to upper case
String letter = Character.toString(text.charAt(x));//extracts character from string and assigns it to another string letter
x++;//increments x by 1 each time
for(int i=0; i<letterA.length; i++)//for loop declares int i = 0, will run while i is less than the the length of the array letterA, and i will increment by 1 each time
{
if(letter.equals(letterA[a][i]))//if the letter is equal to letterA[i]
{
System.out.print (letterA[a][i]);//print out the corresponding letter
break;//breaks from loop
}//end if
else if (letter.equals(" "))//else id the letter is equal to a space
{
System.out.print(" ");//prints out space
break;//breaks from loop
}//end else if
}//end for loop
}//end while loop
}//end main
}//end class

This doesn't work because letterA.length is 3, so your for loop only runs through 3 iterations, instead of 26.

I think you should change your for loop to
for (int i= 0; i < letterA[0].length ; i++ ) {
if (letter.equals(letterA[0][i]) {
System.out.print(letterA[a][i]);
break;
}
else {
// .........,.......
}
}
First use the first array as basis. Compare the letters then if they are equal then get the index of that letter to be used in encrypting
I'm using a bloody phone ryt now so I didn't really compile your code