I am trying to create a code that takes any string and relays it back to me backwards missing every 3rd character and including the very last character.
EX: "123456789" should return "963" &
"Hello, World!" should return "!r lH"
import java.util.Scanner;
public class cypher {
public static void main(String[] args) {
Scanner scnr = new Scanner(System.in);
String str = scnr.nextLine();
String reverse = "";
System.out.println(str.length());
for (int i = str.length() - 1; i >= 0; --i) {
reverse = reverse + str.charAt(i - 3);
}
System.out.println(reverse);
}
}
The code above is what I have so far. However when I run this code I get this error message: "Exception in thread "main" java.lang.StringIndexOutOfBoundsException: String index out of range: -1"
I don't understand because the string length is 10 so why is it not able to do this? Could someone explain this to me and give me a suggestion on how to fix this?
I suggest just iterating the characters in the string, starting from the last position, and moving backwards in increments of 3:
Scanner scnr = new Scanner(System.in);
String str = scnr.nextLine();
String reverse = "";
for (int i=str.length()-1; i >= 0; i=i-3) {
reverse += str.charAt(i);
}
System.out.println(reverse);
Your current approach is failing because the loop just takes single, not triple steps. Also note that you might want to use StringBuilder instead of String to build the reverse string. This might be more efficient (though the JVM itself might substitute StringBuilder on its own).
You current logic is str.charAt(i - 3) and continue while i >= 0. The str.charAt(i - 3) statement will generate java.lang.StringIndexOutOfBoundsException when i is less than 3, thus you should change your code to this.
public static void main(String args[]) {
Scanner scnr = new Scanner(System.in);
String str = scnr.nextLine();
String reverse = "";
System.out.println(str.length());
for (int i = str.length() - 1; i >= 0; i = i - 3) {
reverse = reverse + str.charAt(i);
}
System.out.println(reverse);
}
According to your current logic str.charAt(i - 3) here when value of i becomes less than 3, your code will try to access and index that is a -ve number and thus throws this exception.
You'll have to check if i - 3 >= 0 before using str.charAt(i - 3) else break out of the loop.
I tried this code in my system and it works fine. Try this:
import java.util.Scanner;
public class cypher {
public static void main(String[] args) {
Scanner scnr = new Scanner(System.in);
String str = scnr.nextLine();
String reverse = "";
System.out.println(str.length());
for (int i = str.length() - 1; i>= 0; i-=3) {
reverse = reverse + str.charAt(i);
}
System.out.println(reverse);
}}
Changed your code a little and this works fine now.
You were getting the java.lang.StringIndexOutOfBoundsException because your for loop decremented by a single step every time instead of the required step of 3. As a result when the string has less than 3 characters left the value of variable i becomes negative and an exception is thrown when the charAt(i) function is called with a negative value.
import java.util.Scanner;
public class cypher {
public static void main(String[] args) {
Scanner scnr = new Scanner(System.in);
String str = scnr.nextLine();
String reverse = "";
System.out.println(str.length());
int i = str.length() - 1;
while(i >= 0)
{
reverse = reverse + str.charAt(i);
i-=3;
}
System.out.println(reverse);
}
}
Related
I have created a palindorme java program which is getting an error.the error is saying int cannot be converted to boolean.
import java.util.Scanner;
public class palindrome
{
public static void main()
{
Scanner sc = new Scanner(System.in);
int l,i;
String s,s1;
System.out.println("Enter your string");
s = sc.nextLine();
l = s.length();
for(i=0;l-i-1;i++)
{
s1 = s + s.charAt(i);
}
if(s1==s)
System.out.println("This is Palindrome");
else
System.out.println("This is not a Palindrome");
}
}
For loop condition seems wrong.
for(initial counter; condition to terminate; increase counter) {}
for(i=0; i<l; i++) {}
Along with the answer above you can try a different approach. You don't need to go all the string length to check a palindrome. A palindrome can be checked iterating half of the array length like this -
public void checkPalindrome(String strToCheck){
char[] arr = strToCheck.toCharArray();
int size = arr.length;
char [] original = Arrays.copyOf(arr,arr.length);
for (int i = 0; i < size / 2; i++) {
char temp = arr[i];
arr[i] = arr[size-i-1];
arr[size-i-1] = temp;
}
if(Arrays.equals(arr, original)) {
System.out.println("Palindrome");
} else {
System.out.println("Not a palindrome");
}
}
What are done here:
reversing the string first iterating the halfway
comparing the reversed string with the original using Arrays.equals() method.
There are quite a few things off here, first here is the fixed code:
public static void main(String [] args)
{
Scanner sc = new Scanner(System.in);
int l,i;
String s = "",s1 = "";
System.out.println("Enter your string");
s = sc.nextLine();
l = s.length();
for(i = l - 1; i >= 0; i--)
{
s1 = s1 + s.charAt(i);
}
if(s1.equals(s))
System.out.println("This is Palindrome");
else
System.out.println("This is not a Palindrome");
}
The first thing to fix was your for loop, as you saw you were getting an error. This was fixed by setting the initial i to the length minus 1, changing the loop condition to i >= 0, and using i-- to subtract 1 from i each loop.
These changes to the loop were made so that the character starting from the last position in the String is the first one being return by s.charAt(i) so you can reverse the String. I think you were attempting to do something along these lines to add the characters starting from the end to a String.
I also changed s1 = s + s.charAt(i) to s1 = s1 + s.charAt() so the correct String is being appended. (This should probably be StringBuilder however).
s and s1 now have the initial condition of "" instead of nothing.
And finally you cannot compare String equality with ==, it must be s1.equals(s).
Test Run:
Enter your string
racecar
This is Palindrome
I've searched about everywhere but I just can't find anything very concrete. I've been working on this code for awhile now but it keeps stumping me.
public static void main(String[] args) {
System.out.println(palindrome("word"));
}
public static boolean palindrome(String myPString) {
Scanner in = new Scanner(System.in);
System.out.println("Enter a word:");
String word = in.nextLine();
String reverse = "";
int startIndex = 0;
int str = word.length() -1;
while(str >= 0) {
reverse = reverse + word.charAt(i);
}
}
There's a lot of ways to accomplish this using a while loop.
Thinking about simplicity, you can imagine how could you do this if you had a set of plastic separated character in a table in front of you.
Probably you'll think about get the second character and move it to the begin, then get the third and move to begin, and so on until reach the last one, right?
0123 1023 2103 3210
WORD -> OWRD -> ROWD -> DROW
So, you'll just need two code:
init a variable i with 1 (the first moved character)
while the value of i is smaller than total string size do
replace the string with
char at i plus
substring from 0 to i plus
substring from i+1 to end
increment i
print the string
The process should be:
o + w + rd
r + ow + d
d + row +
drow
Hope it helps
Here is an piece of code I write a while back that uses almost the same process. Hope it helps!
String original;
String reverse = "";
System.out.print("Enter a string: ");
original = input.nextLine();
for(int x = original.length(); x > 0; x--)
{
reverse += original.charAt(x - 1);
}
System.out.println("The reversed string is " +reverse);
public static void main(String[] args) {
Scanner sc=new Scanner(System.in);
int N=sc.nextInt();
String s="";
for(int i=0;i<N;i++){
s=sc.nextLine();
}
Eg : N= 10
S = aabbbabbab
How do I take an input of String of n length ?
I am trying to take an input String which must be of length N.
I know the above logic is wrong, but still i am confused ?
PS: The first line of input contains a single integer N − the length of the string.
The second line contains the initial string S itself.
Check if the input String is greater than the maximumlength.
if (s.length() > maximumLength) { // do something
And what you can do is to use a substring in order to trim the input.
fixedInput = s.substring(0, maximumLength - 1);
Okay, as you are reading the number first, you must initialize maximumLength with the first input.
As an alternative you can ask the user until the input fits the entered length:
do {
s = sc.nextLine();
if (s.length() != maximumLength)
System.out.println("The input did not fit the size");
} while (s.length() != maximumLength);
Use this:
Scanner sc = new Scanner(System.in);
int N = sc.nextInt(); // N == 5 e.g
sc.nextLine(); // Consume the leftover '\n'
String s = sc.nextLine(); // Hello World
s = s.substring(0, N);
System.out.println(s); // Hello
I would suggest to check the input string using an if and return the user to input again if it doesn't match the length that you are looking for.
Example:
if(s.length() != n) {
//Take another input
}
You can do the above in a loop until this condition is satisfied (maybe a while loop).
public static void main(String[] args) {
Scanner sc=new Scanner(System.in);
int n=sc.nextInt();
String s="";
do{
s = sc.nextLine();
}while(s.length() != n);
}
In the above code, all you are doing is reading in n strings, and setting s to the last one (there will also be an exception thrown if there aren't n strings in the input stream). What you need to do is read in a string and compensate for any length errors.
if(in.hasNextLine()) {
s = in.nextLine();
if(s.length() > n) s = s.substring(0, n); // Cut the string so it is of the desired length
else {
for(int i = 0; i < n - s.length(); i++) s += " "; // Add spaces until the string is of the desired length
}
}
I'm trying to write my own Java word count program. I know there may already be a method for this, but I'd like to get it work. I'm getting an out of bounds error at line 14. I'm trying to use an input word to count how many times it appears in an input string. So I'm looping up to stringlength - wordlength, but that's where the problem is.
Here is the code:
import java.util.Scanner;
public class wordcount {
public static void main(String[] args)
{
Scanner s = new Scanner(System.in);
System.out.print( "Enter word : " );
String word = s.nextLine();
Scanner t = new Scanner(System.in);
System.out.print("Enter string: ");
String string = t.nextLine();
int count = 0;
for (int i = 0; i < string.length()-word.length(); i = i+1){
String substring = string.substring(i,i+word.length());
if (match(substring, word)==true){
count += 1;
}
}
System.out.println("There are "+count+ " repetitions of the word "+word);
}
public static boolean match(String string1, String string2){
for (int i=0; i<string1.length(); i+=1){
if (string1.charAt(i)!=string2.charAt(i)){
return false;
}
}
return true;
}
}
First of all, two Scanners are not necessary, you can do many inputs with the same Scanner object.
Also, this if condition
if (match(substring, word) == true)
can be rewritten like
if (math(substring, word))
I would also recommend you to use i++ to increase the loop variable. Is not strictly necessary but is "almost" a convention. You can read more about that here.
Now, about theIndexOutOfBoundsException, I've tested the code and I don't find any input samples to get it.
Besides, there is an issue, you are missing one iteration in the for:
for (int i = 0; i < string.length() - word.length() + 1; i++) { // Add '+ 1'
String substring = string.substring(i, i + word.length());
// System.out.println(substring);
if (match(substring, word)) {
count++;
}
}
You can test it by putting a print statement inside the loop, to print each substring.
I'm not getting an out of bounds error, can you tell me what values you were using for word and string?
I have identified a bug with your program. If word is equal to string, it still returns count 0. I suggest adding one more iteration and using regionMatches instead. RegionMatches makes your match method obsolete and will return false if word.length() + i is equal or greater than string.length(), avoiding out of bounds issues.
As you can see I also moved the calculations to a seperate method, this will make your code more readable and testable.
And as Christian pointed out; you indeed do only need one Scanner object. I've adapted the code below to reflect it.
public static void main(String[] args) {
Scanner sc = new Scanner(System.in);
System.out.print("Enter word : ");
String word = sc.nextLine();
System.out.print("Enter string: ");
String string = sc.nextLine();
int count = calculateWordCount(word, string);
System.out.println("There are " + count + " repetitions of the word " + word);
}
private static int calculateWordCount(String word, String string) {
int count = 0;
for (int i = 0; i < string.length() - word.length() + 1; i++) {
if (word.regionMatches(0, string, i, word.length())) {
count++;
}
}
return count;
}
So I'm trying to find all the uppercase letters in a string put in by the user but I keep getting this runtime error:
Exception in thread "main" java.lang.StringIndexOutOfBoundsException:
String index out of range: 4
at java.lang.String.charAt(String.java:686)
at P43.main(P43.java:13)
I feel foolish but I just can't figure this out and oracle even talks about charAt on the page about java.lang.StringIndexOutOfBoundsException
Here is my code for finding the uppercase letters and printing them:
import java.io.*;
import java.util.*;
public class P43{
public static void main(String[] args){
Scanner in = new Scanner(System.in);
//Uppercase
String isUp = "";
System.out.print("Please give a string: ");
String x = in.next();
int z = x.length();
for(int y = 0; y <= z; y++){
if(Character.isUpperCase(x.charAt(y))){
char w = x.charAt(y);
isUp = isUp + w + " ";
}
}
System.out.println("The uppercase characters are " + isUp);
//Uppercase
}
}
I'd really appreciate any input and or help.
for(int y = 0; y <= z; y++){
should be
for(int y = 0; y < z; y++){
Remember array index starts from ZERO.
String length returns
the number of 16-bit Unicode characters in the string
Because loop started from ZERO, loop should terminate at length-1.
The array index out of bounds is due to the for loop not terminating on length - 1, it is terminating on length
Most iterating for loops should be in the form:
for (int i = 0; i < array.length; i++) {
// access array[i];
}
It's the same with a string.
Perhaps a cleaner way would be:
String inputString; // get user input
String outputString = "";
for (int i = 0; i < inputString.length; i++) {
c = inputString.charAt(i);
outputString += Character.isUpperCase(c) ? c + " " : "";
}
System.out.println(outputString);
Edit: Forgot String Doesn't implement Iterable<Character>, silly Java.
With Java 8 you can also use lambdas. Convert the String into a IntStream, use a filter to get the uppercase characters only and create a new String by appending the filtered characters to a StringBuilder:
Scanner in = new Scanner(System.in);
System.out.print("Please give a string: ");
//Uppercase
String isUp = in.next()
.chars()
.filter(Character::isUpperCase)
.collect(StringBuilder::new, // supplier
StringBuilder::appendCodePoint, // accumulator
StringBuilder::append) // combiner
.toString();
System.out.println("The uppercase characters are " + isUp);
//Uppercase
Inspired by:
Adam Bien - Streaming A String
Simplest way to print anIntStream as a String
Try this...
Method:
public int findUpperChar(String valitateStr) {
for (int i = valitateStr.length() - 1; i >= 0; i--) {
if (Character.isUpperCase(valitateStr.charAt(i))) {
return i;
}
}
return -1;
}
Usage:
String passwordStr = password.getText().toString();
.......
int len = findUpperChar(passwordStr);
if ( len != -1) {
capitals exist.
} else {
no capitals exist.
}
Hi one of the easy step to find uppercase char in a given string...
Program
import java.io.*;
public class testUpper
{
public static void main(String args[]) throws IOException
{
String data,answer="";
BufferedReader br=new BufferedReader(new InputStreamReader(System.in));
System.out.println("Enter any String : ");
data=br.readLine();
char[] findupper=data.toCharArray();
for(int i=0;i<findupper.length;i++)
{
if(findupper[i]>=65&&findupper[i]<=91) //ascii value in between 65 and 91 is A to Z
{
answer+=findupper[i]; //adding only uppercase
}
}
System.out.println("Answer : "+answer);
}
}
Output
Enter any String :
Welcome to THe String WoRlD
Answer : WTHSWRD
You can increase the readability of your code and benefit from some other features of modern Java here. Please use the Stream approach for solving this problem. Also, I suggest importing the least number of libraries into your class. Please avoid using .* while importing.
import java.util.Scanner;
public class P43 {
public static void main(String[] args) {
Scanner in = new Scanner(System.in);
System.out.print("Please give a string: ");
String x = in.next();
x.chars().filter(c -> Character.isUpperCase(c))
.forEach(c -> System.out.print((char) c + " "));
}
}
Sample input:
saveChangesInTheEditor
Sample output:
C I T E
import java.util.Scanner;
class Demo
{
public static void main(String[] args)
{
StringBuilder s=new StringBuilder();
Scanner input = new Scanner(System.in);
System.out.println("Enter your String");
String str= input.nextLine();
for(int i=0; i<str.length(); i++)
{
if(Character.isUpperCase(str.charAt(i)))
{
System.out.print(str.charAt(i)+" ");
}
}
}
}
The simplest way I know is to use regex replacement.
isUp = x.replaceAll("[^A-Z]", "");
In simple terms, this uses a regular expression which matches any character which is not in the A-Z range, and replaces it with an empty string.
public static void main(String[] args) {
Scanner input = new Scanner(System.in);
System.out.println("Enter the number");
String str= input.nextLine();
int ascii;
for(int i=0; i<str.length(); i++) {
ascii = str.charAt(i);
System.out.println(ascii);
if (ascii >= 65 && ascii <= 90) {
System.out.println("captal letter found ::: "+ascii);
}
}
}
public class Cama {
public static void main(String[] args) {
String camal = "getStudentByName";
String temp = "";
for (int i = 0; i < camal.length(); i++) {
if (Character.isUpperCase(camal.charAt(i))) {
System.out.print(" " + Character.toLowerCase(camal.charAt(i)));
} else if (i == 0) {
System.out.print(Character.toUpperCase(camal.charAt(i)));
}else{
System.out.print(camal.charAt(i));
}
}
}
}