I need to concatenate output from a loop. User input will determine for how long it will last. I'm am trying to generate a password with generating a random number and then converting the number into ASCII character (all lowercase characters currently). Instead of having multiple for() how is it possible to concatenate the out put into one string based on the user input?
import java.util.Random;
import java.util.Scanner;
public class Password
{
public static void main (String[] args)
{
int randNum=0;
int min=97;
int max=122;
int az=0;
String b="";
String c="";
Scanner in= new Scanner (System.in);
Random randNumlist= new Random();
System.out.println("lowercase letters [a]");
String input= in.next();
System.out.println(" how many characters (max 14)");
int input2=in.nextInt();
if ( input.equalsIgnoreCase("A"))
{
while(!(randNum>=96 && randNum<=123))
{
for (int n=1; n <=input2; n++)
{
randNum= randNumlist.nextInt((max-min)+1)+min;
az =+randNum;
char p= (char)az;
b = new StringBuilder().append("").append(p).toString();
System.out.println(b);
}
}
}
}
}
Example input: a or A
2nd Example input: numbers 1-14
Example output:
a
e
b
h
Desired output: aebh
Several points:
Your for loop is pointless. You initialise n to input2 then loop until n == input2 meaning one iteration
Your while loop is pointless and will only also iterate once as randNum is set to between 96 and 123 in the first iteration
Declare your StringBuilder outside of the loop. Currently you create one for each iteration (which is only once) which means the previous String will be lost. Then in your loop just call the append method.
Print after the loop by calling the toString() method of your StringBuilder.
So something like this
StringBuilder sb = new StringBuilder()
//Start Loop
sb.append("Your character here");
//End Loop
System.out.println(sb.toString());
Related
My assignment is to write a program to scramble a word while maintaining the same first and last letter and only swapping two letters, then prompt the user to continue if they wish.
Example: userInput = bacon | Output = bcaon
I've attached an imagine of my program, there may be several issues, but as it stands I can't really run it due to the errors in the image. I'm really confused because I got a TA to help me on this assignment, and they seemed to think this would definitely work, but as you can see it does not.
I would really appreciate if someone could tell me what exactly is wrong and why. And if you have anything to add to make this program work, I'd really, really appreciate that too, but bottom line is I just want to understand what's wrong and why.
import java.util.Scanner;
import java.util.Random;
public class FreeStyle {
public static void main(String[] args) {
Scanner in = new Scanner(System.in); // Importing and initializing keyboard to 'in'
System.out.println("Please enter a word to be scrambled"); // Asking user for a word
String word = in.next(); // Initializing the user's input
System.out.println(swapLetters(word));
System.out.println("Would you like to enter another word? y/n");
String answer = in.next();
boolean userDone = true; //Using a Boolean statement to ask the user if they are done enter words or not
while (userDone) {
if (answer.equals('y')) {
System.out.println("Please enter a new word"); //Ask user for new word to scramble
word = in.nextLine(); //New initialization for 'word'
} else if (answer.equals('n')) { //If user types 'n', loops then breaks because while(userDone) is false
userDone = false;
} else {
System.out.println("Invalid input, please enter more than 3 letter words."); // The logic doesn't flow or apply to words that are less than 4 letters, so this catches that error and notifies the user
}
}
}
private static String swapLetters(String word) { //Private method used for the program only, no need to involve the user
Random r = new Random(); //Using random instead of math floor
//int arraysize = word.length();
int a = r.nextInt(word.length()-2)+1;
int b = r.nextInt(word.length()-2)+1;
//String word2 = word.substring(a, a+1);
String word2 = word.substring(0, a) + word.charAt(b)+word.substring(a+1, b)+word.charAt(a)+word.substring(b+1);
return word2;
}
Several points:
Why not use something already done exactly for what you are trying to do - Collections.shuffle? See comments in the code for understanding how it works.
You can't use equals() between a String and a char (' ' are for chars, " " are for Strings). Simple fix - just put your 'y' into "y", same for 'n'.
I've refactored the code at the beginning that we used to get user input and then scramble into a separate method, so we can reuse it again - getInputAndScramble.
And finally, I've used a do-while loop to keep looping until the user stops the loop with the "n" letter.
Please see my comments in the code, hopefully will clear things up.
public class Scrambler {
public static void main(String[] args) {
boolean userDone = true;
String word;
Scanner in = new Scanner(System.in);
getInputAndScramble(in); //Extracted method to get Scanner input and scramble
do {
System.out.println("Would you like to enter another word? y/n");
word = in.next();
while (userDone) {
if (word.equals("y")) {
getInputAndScramble(in);
break;
} else if (word.equals("n")) {
userDone = false;
} else {
System.out.println("Invalid input, please enter more than 3 letter words.");
}
}
} while (userDone); //continue until "n"
}
private static void getInputAndScramble(Scanner in) {
System.out.println("Please enter a word to be scrambled");
String word = in.next();
System.out.println(swapLetters(word));
}
private static String swapLetters(String word) {
/* Convert word into an ArrayList of characters.
Create ArrayList size of word,
convert String word into a char array and insert every char in
the char array into our ArrayList.
*/
ArrayList<Character> chars = new ArrayList<>(word.length());
for (char c : word.toCharArray()) {
chars.add(c);
}
//Shuffle, omitting first and last letters
Collections.shuffle(chars.subList(1, chars.size()-1));
//Add shuffled letters into an array to output as a word entity
char[] shuffled = new char[chars.size()];
for (int i = 0; i < shuffled.length; i++) {
shuffled[i] = chars.get(i);
}
//Return shuffled String
return new String(shuffled);
}
}
You are assuming that the two random number a and b have the property that a < b. What if a >= b? Then word.substring(a+1, b) will throw an error.
To fix it, just make sure that a < b is maintained (regenerating, swapping, etc.).
But to be sure, there are more than just this bug in your code. For example, using next(), comparing String with char, using wrong newline character, not striping newline character, and so on. You might want to add some print statements in your code you see what is actually happening.
Well, as for the swapping function, something like that should work:
private static String swapLetters(String word) {
char[] temp = word.toCharArray();
char swapHelper;
Random r = new Random();
int a = r.nextInt(word.length()-2)+1;
int b = r.nextInt(word.length()-2)+1;
swapHelper = temp[a];
temp[a] = temp[b];
temp[b] = swapHelper;
word = String.copyValueOf(temp);
return word;
}
Basically, im converting string to char array so i can operate on them with ease. A and B are variables that contain index of letters that should be swapped. After that, array is converted back to string and returned.
I'm trying to make a short program that converts any string into T H I S F O N T.
For example: "This is a test sentence" turns into "T H I S I S A T E S T S E N T N C E"
I have a StringBuilder inside a while loop, but using finale.insert(i, '\t'); doesn't work.
import java.util.Scanner;
public class Executable {
public static void main(String[] args) {
Scanner input = new Scanner(System.in);
String x;
int i = 0;
System.out.print("Input text here: ");
x = input.nextLine();
StringBuilder finale = new StringBuilder(x.toUpperCase());
while(i > finale.length()) {
if(finale.substring(i, i) == " ") {
i += 2;
finale.insert(i, '\t');
}
}
System.out.println(finale);
}
}
Any help?
You have a few issues with your code. Before I present an implementation that works, let's look at those other issues.
Your while loop checks if i > finale.length(). Since i = 0 the while loop never has a chance to begin.
You are comparing strings using == and this is not correct. == is used to confirm two objects are equal, not the value of two strings. You would need to use string.equals() instead.
You're doing too much in your loop anyway. Using a simple for loop can accomplish the goal quite simply.
Here is a new loop you can use instead of what you have:
for (int i = 1; i < finale.length(); i++) {
finale.insert(i++, " ");
}
The output: T H I S F O N T
For those unfamiliar with for loops, here's a very simple breakdown of how the above is structured.
The for loop is defined in three parts:
for (variable_to_increment; repeat_until_this_condition_is_met; modify_variable_on_each_iteration) {
// Code to be executed during each pass of the loop
}
First, we define a variable that we can track on each loop: int i = 1. By setting i = 1, we are going to skip the first character in the string.
The next statement, i < finale.length() means that we want to keep repeating this loop until we reach the length of our string. For example, if the string is 5 characters long and we've run the loop 4 times, i now equals 5 and is no longer less than the string's length, so the loop ends.
The last part is i++. This tells Java what we want to do with i after each loop. In this case, we want to increment the value by 1 each time the loop repeats.
Everything inside the brackets is, obviously, the code we want to execute on each loop.
You're saying while i>finale.length() but i is initialized as 0. You never enter the while loop.
Some issues with your code (see inline comments):
import java.util.Scanner;
public class Executable {
public static void main(String[] args) {
Scanner input = new Scanner(System.in);
String x;
int i = 0;
System.out.print("Input text here: ");
x = input.nextLine();
StringBuilder finale = new StringBuilder(x.toUpperCase());
while(i > finale.length()) { // this condition is incorrect. Initially
// this condition will always be false
// if you input some sentence. It should be
// i < finale.length()
if(finale.substring(i, i) == " ") { // here preferably you should use
// equals method to compare strings
i += 2;
// you are only incrementing the i if the ith
// substring equals " ". Firstly, substring(i,i)
// will return empty string because the second argument
// is exclusive
finale.insert(i, '\t');
}
}
System.out.println(finale);
}
}
If you want to have an alternate method (not very optimal) for doing what you want to do, you can try the following approach:
import java.util.Scanner;
public class Executable {
public static void main(String[] args) {
Scanner input = new Scanner(System.in);
String x;
int i = 0;
System.out.print("Input text here: ");
x = input.nextLine();
String finale = x.toUpperCase().replaceAll(" ","").replaceAll("", " ");
System.out.println(finale);
}
}
First, convert the string to uppercase --> then remove all spaces between the words --> then insert spaces between all letters. The code line which does this is,
String finale = x.toUpperCase().replaceAll(" ","").replaceAll("", " ");
Here is a sample run:
Input text here: This is a sentence
T H I S I S A S E N T E N C E
The correct way with your method would be, just increment until you have twice the size of the initial String
while (i < x.length() * 2) {
finale.insert(i, '\t');
i += 2;
}
An easier way would be with a classic for-loop:
StringBuilder finale = new StringBuilder();
for (char c : x.toUpperCase().toCharArray()) {
finale.append(c).append('\t');
}
Use a for loop since you know the number of iterations:
Scanner input = new Scanner(System.in);
String x;
System.out.print("Input text here: ");
x = input.nextLine();
StringBuilder finale = new StringBuilder(x.toUpperCase());
int len = finale.length();
for (int i = 1; i < 2 * len; i+=2 ) {
finale.insert(i, '\t');
}
System.out.println(finale);
You are comparing strings with ==. Never do that; use equals instead.
For future readers: this job can be done elegantly using Java 8 Streams:
String result = str.chars()
.filter(i -> i != ' ')
.mapToObj(t -> (char) t)
.map(Character::toUpperCase)
.map(Character::valueOf)
.collect(Collectors.joining(" ");
I am exercising for my course in java and the task is to write a program which has the input of a list separeted with spaces. And the key is to turn the list around, i.e. put the first place on the last second on the one before last and truncate the negatives. But I am keep getting this error of StringIndexOutOfBounds. What seems to be the problem?
public static void main(String args[])
{
Scanner in = new Scanner (System.in);
System.out.println("Insert the list: ");
String input = in.nextLine();
String out = out(input);
System.out.println(out);
}
public static String out (String input){
String reverse = "";
int counter = 0;
while (counter<=input.length()){/*
String min = input.charAt(counter) + input.charAt(counter+1);
int num = Integer.parseInt(min) ;
if ( num>=0 ){*/
reverse+= input.charAt(counter);
counter++;
/*}*/
}
return reverse;
}
I suspect your StringIndexOutOfBounds comes from the fact you are iterating from index 0 to index input.length, so 1 too many.
For the sake of charAt the Strings in Java are 0-indexed, so you start counting from 0 (what you would call 'first' in plain English). In such a situation, the last character is at index length-1.
So, to be specific. Your next thing to fix is the condition in the while loop. I think your intention was to say:
while (counter < input.length()) {
...
Any String has characters from index 0 to length-1. If you would try to do charAt(length), you would end up with StringIndexOutOfBounds.
Change the while line to below & it should work:
while (counter<input.length()){
First of all, i just started programming with Java so i'm really a noob :P
Ok so my instructor gave me an assignment which is to take an int input from the user and put each digit in a new line.
for example, if the user gave 12345, the program will give:
1
2
3
4
5
each number in a new line.
The statements i will be using is IF statement and the loops and operators ofcourse.
I thought about using the % operator inside the IF/WHILE but i have two issues. One is that i don't know the number of digits the user is inputting and since i can't use the .length statement i reached a dead end. second of all the console output will be 5 4 3 2 1 inversed.
So can anyone help me or give me any ideas?
import java.util.Scanner;
public class NewLineForDigit {
public static void main(String[] args) {
System.out.print("Please, enter any integer: ");
Scanner sc = new Scanner(System.in);
String intString = sc.next();
for (char digit : intString.toCharArray()) {
System.out.println(digit);
}
}
}
Given the assignment your instructor gave you, can you convert the int into a String? With the input as a String, you can use the length() String function as you had mentioned to iterate the number of characters in the input and use the built-in String function charAt() to get the index of character you want to print. Something like this:
String input = 12345 + "";
for(int i = 0; i < input.length(); i++)
System.out.println( input.charAt(i) );
How about using a Scanner to get the users input as an int and converting that int to a String using valueOf. Lastly loop over the String to get the individual digits converting them back to int's from char's :
import java.util.Scanner;
class Main {
public static void main(String[] args) {
Scanner sc = new Scanner(System.in);
System.out.print("Please enter a Integer:");
int input = sc.nextInt();
String stringInput = String.valueOf(input);
for(int i = 0; i < stringInput.length(); i++) {
int j = Character.digit(stringInput.charAt(i), 10);
System.out.println(j);
}
}
}
Try it here!
So I'm new to programming. I'm using java. Right now I have an assignment I can't solve on a website that teaches java.
This is the assignment
Write a program that returns number of occurrences of a string in another string.
E.g
Input:
First String: the
Second String: The children are playing with their toys because they love it.
Output:
3
Note: You should only use nested loops. Don’t use methods like indexOf or substring.
public static void main(String[] args) {
Scanner input = new Scanner (System.in);
String a = input.nextLine();
String b = input.nextLine();
String z[] = b.split(" ");
int number=0;
for (int i =0; i<z.length; i++){
if (z[i].contains(a))number++;
}
System.out.println(number);
I won't give you too much code, but here are the main talking points:
You need a way to read the input in. This can be accomplished with a Scanner - it's either from STDIN or a file.
You need a way to break up each word in the sentence. String#split will help you with that.
You need a way to ignore the casing of each sentence - toLowerCase() works well here.
You need to loop over each word in one sentence, as well as each occurrence in the other sentence. Consider that String.split produces a String[], and you can iterate over that with any standard for loop.
You need a way to see is a string is contained in another string. String#contains will help - although you want to be very careful on which side you're asking contains a string. For example:
// This will print true
System.out.println("The world".toLowerCase().contains("the"));
// This will print false
System.out.println("the".contains("The world".toLowerCase()));
Try this :
import java.util.Scanner;
public class Occurence {
/**
* #param args
*/
public static void main(String[] args) {
Scanner input = new Scanner(System.in);
String str1 = input.nextLine();
String str2 = input.nextLine();
int count = 0;
String word[] = str1.split(" ");
for (int i = 0; i < word.length; i++) {
if (word[i].toLowerCase().contains(str2.toLowerCase())) {
count++;
}
}
System.out.println("Occurence = " + count);
}
}