I am a first year c.s student, but I am having trouble making this program fit my teacher's requirement. The program will receive a string and an integer that will create this:
Please enter a string: ThisIsAnExample
Please enter an integer: 3
Thi
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He wants the for loop to be inside a method called splitter. The splitter method should have two parameters, a string and an int, for inputStr and inputInt.
Here is what I have so far:
public static void main(String[] args) {
Scanner keyboard = new Scanner(System.in);
System.out.print("Please enter a string: ");
String inputStr;
inputStr = keyboard.nextLine();
System.out.println("Please enter an integer: ");
int inputInt;
inputInt=keyboard.nextInt();
for(int i =0;i<inputStr.length();i+=inputInt){
if(i+inputInt < inputStr.length())
System.out.println(inputStr.substring(i,i+inputInt));
else
System.out.println(inputStr.substring(i,inputStr.length()));
}
}
If the splitter method is to actually just print the stuff to standard output, start with:
static void splitter (String inputStr, int inputInt) {
}
and call it with:
splitter (inputStr, inputInt);
once you have those values in your main method.
Then it's a simple matter of moving some of your code from main() into splitter().
If you wanted to return the string array and print it from main(), you could use:
static String[] splitter (String inputStr, int inputInt) {
}
and call it with:
String[] bits = splitter (inputStr, inputInt);
// print the array here.
This would be a more flexible case if you ever wanted to do something other than just print it. For an assignment at this level though, it's probably okay to just print within the method itself.
You need to create a function, apparently.
To use a method/function, a few things need to be done:
You need to write the body of your function :
public void splitter(String myStringArg,int myIntArg){
// Your code ....///}
Finally, you need to call your function. In your main :
splitter(myString,myInt);
In the splitter body, you'll be able to use myStringArg; you will supply its value by calling.
So, in splitter :
myStringArg = myString (in value).
Good luck!
Related
I'm learning to code Java with mooc at the moment and am doing an assignment where you take user input (and do stuff with it). The program/loop ends if user inputs nothing and enters.
So this is the right answer which I did correctly:
while (true) {
String sentence = scanner.nextLine();
if (sentence.equals("")) {
break;
}
}
However before this I also tried something like:
while (!scanner.nextLine().equals("")) { // ...
Why does that method not work? I don't see anything wrong with it.
(Below is the whole code if needed)
import java.util.Scanner;
public class AVClub {
public static void main(String[] args) {
Scanner scanner = new Scanner(System.in);
while (!scanner.nextLine().equals("")) {
String sentence = scanner.nextLine();
String[] array = splitter(sentence);
for (int i = 0; i < array.length; i++) {
if (array[i].contains("av")) {
System.out.println(array[i]);
}
}
}
}
public static String[] splitter(String sentence) {
String[] array = sentence.split(" ");
return array;
}
}
Try using scanner.hasNext() to see if there is anything else that you can read in. Instead of your splitter method, you can use StringTokenizer which will tokenize the String by spaces.
The reason your code does not work is because you are calling Scanner.nextLine() twice. Even though your code:
while (!scanner.nextLine().equals(""))
is a condition check, it reads it in and moves on. Think about it like this: The Scanner is like a book reader. When you call Scanner.nextLine(), the book reader moves to that line and reads it. When you called it again, it read an empty line. For example, if I input this:
Your reader will read in the "I like pie" and check to see that it is not a "". When it is done, and you get your sentence variable, you called the method again, which reads in the NEXT line, which is not there. So your code fails to work.
I am a java beginner, and in this particular problem I practiced making a program that converts any given string to lowercase string. Is there a a better way to achieve this goal in java (in terms of design)?
Also, how does the "else" (after "else if") catches or waits for me to make an input. Somehow that part does not make sense to me, even though I achieved what I wanted. How is the value of "ans" from input transferred to the entire loop and used until the loop is closed?
After many attempts and failures, I used a separate method for the conversion part. My second question is a bit too complicated to be researched.
import static java.lang.System.out;
import java.util.Scanner;
public class MyClass {
public static Scanner s = new Scanner(System.in);
public static String ans;
public static void main(String args[]) {
Conversion();
do {
ans = new String(s.nextLine());
if (ans.equalsIgnoreCase("Y")) {
Conversion();
} else if (ans.equalsIgnoreCase("N")) {
out.println("Thank you for using this program!");
break;
} else {
out.println("Invalid entry!");
out.println("Would you like to convert another string?\n(Please type 'Y' for yes, or 'N' for no.)");
}
} while (ans != "N");
}//END MAIN
public static void Conversion() {
out.println("Please enter string to be converted to lowercase: ");
String str = new String(s.nextLine());
out.println("Your new string is: " + str.toLowerCase());
out.println("Would you like to convert another string? (Y/N)");
}
}
I notice a few issues; Conversion looks like a class-name (Java naming convention would be conversion) and ans != "N" is using == instead of .equals - and wouldn't ignore case (!ans.equalsIgnoreCase("N")). Globals (e.g. static) are bad (pass the Scanner to the methods that need it), and the static import just makes the code more difficult to reason about (in my opinion). Your current loop doesn't really follow a conventional form, I would extract the prompt and loop for "another" conversion to a new method and if you must print a thank you I'd do so after the "main loop". Something like,
public static void main(String args[]) {
Scanner sc = new Scanner(System.in);
do {
conversion(sc);
} while (another(sc));
System.out.println("Thank you for using this program!");
}
public static void conversion(Scanner s) {
System.out.println("Please enter string to be converted to lowercase: ");
System.out.printf("Your new string is: %s%n", s.nextLine().toLowerCase());
}
public static boolean another(Scanner s) {
while (true) {
System.out.println("Would you like to convert another string? (Y/N)");
String ans = s.nextLine();
if (ans.equalsIgnoreCase("Y")) {
return true;
} else if (ans.equalsIgnoreCase("N")) {
return false;
}
System.out.println("Invalid entry!");
System.out.println("(Please type 'Y' for yes, or 'N' for no.)");
}
}
Answering your first question:
There are many design patterns and practices so many people can argue what I would recommend you to do. It's basically the same for all programming languages. Let's take your function "Conversion". The name itself says that you use it to convert stuff. Not to display, not to prompt - to convert. In this case, the only actual thing it should do is to convert upperCase to lowercase. In fact, you might want to specify what type of conversion it has in the name of the function (convertToLowerCase?). In fact, in Java, we use lowerCamelCase for all function names and UpperCamelCase for classes.
If you accept my previous suggestion, you could break the Conversion function into multiple ones like promptUserForInput, WrongInputHandler and so forth.
If I understood your second question correctly, you wonder about the way the code executed and how the variable ans is transferred further into the loop. Let's take a look at your code and what variables do:
You initialize your variable in the class MyClass by making it accessible to all methods in the class;
You prompt the user for the input to assign to this variable inside the do..while loop with this line ans = new String(s.nextLine()); which saves the value of the variable and, again, which can be accessed inside the whole class so its value is changed.
It goes into the if..else if...else statement. The way it works, it goes line by line - if the first if-statement fails, it goes on until it finds a truthy statement and it doesn't go any further. In your case, if the ans is not equal to either y/Y/ it will go to else if statement and if it's not n/N, it will go to else (so basically whatever except y/Y/n/N) and will be executed. After that, it jumps into the while (ans!= "N"); line where it compares your class-member variable ans and if it's not equal to "N" it starts over the loop right after the do{ part until you type in the "N".
I hope that makes sense. Whenever the program is asking you for input, it does not execute code further but is stuck until you provide any input. The value from input itself isn't passed throughout the loop and the program. The reason why you can use it because you created a higher-scope variable ans where you saved the result of your input.
IMPORTANT: if you've declared the ans inside the do..while loop, you would've not been able to have accessed it in the while (ans...) because it will 'die' right before the curly brace between do { ...here} while(). If you want to learn more about the scope and variables in general, you can read this article.
Here is my code example:
public static void main(String args[]) {
//declare before entering the loop to have higher scope
String ans = "y";
do {
//we get the given string to convert from the user
String str = promptForString();
//we convert the string
str = converseStringToLowerCase(str);
//display the string (could use another function for that: easier to debug and locate problems and in bigger projects)
out.println("Your new string is: " + str);
//prompt user for respond to continue or not
ans = promptForContinue();
handleResponse(ans);
} while (!ans.equals("n"));
}//END MAIN
//prompts user for an input string
public static String promptForString() {
out.println("Please enter string to be converted to lowercase: ");
String str = new String(s.nextLine());
return str;
}
//converts any given string to lower case
public static String converseStringToLowerCase(String str) {
return str.toLowerCase();
}
//is used to prompt user for reply
public static String promptForContinue() {
out.println("Would you like to convert another string? (Y/N)");
String str = new String(s.nextLine());
//is good to make if...else statements easier - it will always be lower case (or upper if you prefer)
return str.toLowerCase();
}
//easier to locate other response scenarios
public static void handleResponse(String response) {
if (response.equals("n")) {
out.println("Thank you for using this program!");
//it's not a very good practice to innaturally break loops. Use input for that in while(..) statement
// break;
} else if (!response.equals("y")) {
out.println("Invalid entry!");
out.println("Would you like to convert another string?\n(Please type 'Y' for yes, or 'N' for no.)");
}
}
I implemented a java program with some methods. Next I created a main class which will call the related method by entering a word.
for example:
Enter {A|B|C|D|E} to call method. A=method one B = method two...etc
A<--this is the user input
Enter Number:<--the first Scanner input of method A
123<--Input 1
Enter words:<-- the second Scanner input of method A
ABC<--Input 2
123ABC<--The output method A
Enter {A|B|C|D|E} to call method. A=method one B = method two...etc
B<--this is the user input
Enter Number 1:<--the first Scanner input of method B
100<--Input 1
Enter Number 2:<-- the second Scanner input of method B
50<--Input 2
150<--The output method B
Code of Method A {
String output;
private static Scanner keyboard = new Scanner(System.in);
System.out.println("Enter Number:");
String no = keyboard.nextLine();
System.out.println("Enter Words:");
String words = keyboard.nextLine();
//do something...
System.out.println(output);
}
Code of Main class{
private static Scanner keyboard = new Scanner(System.in);
public static void main(String[] args){
Main main = new Main();
main.run();
}
public void run() {
boolean running = true;
while (running) {
displayMenu();
String command = keyboard.nextLine();
String[] parts = command.split("^");
if ("A".equalsIgnoreCase(command)) {
//call method A
} else if ("B".equalsIgnoreCase(command)) {
//call method B
} else if....etc
System.out.println();
}
what I want is input
A123 , ABCB100,50 at once
then the system will print the output of method A (123ABC) and B (150) for me.
What I want is input A into "keyboard", input 123 into "no" and input ABC into "words" at once
How can I do it?
As long as your don't close your Scanner (or its underlying input stream), the yet-to-read tokens will remain accessible for later use : read two lines (or 4 tokens - the comma is one) and "B\n100,50" will remain.
If you're asking how to provide this kind of input, it depends on your invokation method. If executed from bash, I'd use the following :
echo """A
123 , ABC
B
100,50""" | java ...
If you're asking how to dynamically invoke a method from its name, check the reflection API. Oracle's tutorial is a good resource in my opinion, here's a link to its section on retrieving and invoking methods.
There are 2 ways to do that.
First:
Instead of giving input directly in the console, first write all the data input somewhere and just copy it and paste it in the console.
Second:
You can use hasNexLine() and send EOF through keyboard by pressing ctrl+d.
Code:
public static void main(String[] args)
{
Scanner s = new Scanner(System.in);
StringBuilder sb = new StringBuilder();
while(s.hasNextLine())
{
sb.append(s.nextLine());
}
System.out.println(sb.toString());
}
Provide all your input and press ctrl+d to stop taking input.
I'm trying to create my own methods to use in my main method. I have asked the user for input in my main method and have captured it using next line. However, I am unable to use it in my other methods.
static Scanner keyboard = new Scanner(System.in);
public static void main (String[] args) {
System.out.println("Input string of any length");
String s = keyboard.nextLine();
System.out.println("If you want to the program to check if palindrome, type 1."+
" If you want the program to compute rounded sum, type 2. If you want " +
"the program to count unique characters, type 3");
String o = keyboard.nextLine();
if (o.equals("1"))
System.out.println(isPalindrome());
}
public static boolean isPalindrome () {
boolean palindrome = true;
String s = keyboard.nextLine();
It is asking me to redefine string s, in my other method, even though it has already been defined in the main.
This is because of variable scope. Each variable only exists in a certain part of the program and other parts can have different variables with the same name that only exist in that part.
There are plenty of tutorials around on the subject. For example:
http://docs.oracle.com/javase/tutorial/java/javaOO/variables.html
http://www.java-made-easy.com/variable-scope.html
http://www.cs.berkeley.edu/~jrs/4/lec/08
Adding on to Tim B's answer, it is always good to make a function full and sound.
i.e. instead of
public static boolean isPalindrome ()
Use
public static boolean isPalindrome (String text)
and pass in the text you want to check for palindrome. This makes the function more complete. Treat a function like asking someone a question. "Is this text a Palindrome?" instead of "Is Palindrome?".
I'm doing a simple program regarding methods.
But I have one problem. Everything is already working except when looping.
When I choose to loop again. The program skips on inputting the name. And proceeds directly to the year and section.
Here's the code:
public static void main(String[] args) {
do{
System.out.println("Input info:");
name=stringGetter("Name: ");
yearandsec=stringGetter("Year and section: ");
sex_code=charGetter("Sex code: " + "\n" + "[M]" + "\n" + "[F]:");
scode=intGetter("Scholarship code: ");
ccode=intGetter("Course code: ");
units=intGetter("Units: ");
fee_per_unit=doubleGetter("Fee per unit: ");
misc=doubleGetter("Miscellaneous: ");
display();
switches(scode, units, fee_per_unit, misc);
System.out.println("Another?");
dec=rew.nextInt();
}while(dec==1);
}
Here's the method getting the value for name together with the year and section:
public static String stringGetter(String ny){
String sget;
System.out.println(ny);
sget=rew.nextLine();
return sget;
}
I'm really annoyed with this problem, and I don't have any idea on how to fix this. Please help. thanks
Here is a simpler and more complete program that reproduces the error:
public static Scanner rew = new Scanner(System.in);
public static void main(String[] args) {
int dec;
do {
System.out.println("Input info:");
String name=stringGetter("Name: ");
String yearandsec=stringGetter("Year and section: ");
dec=rew.nextInt();
} while(dec==1);
}
public static String stringGetter(String ny){
System.out.println(ny);
return rew.nextLine();
}
The problem is that after calling nextInt() the call to nextLine() reads up to the new line after the int (giving a blank line), not up to the next new line.
If you change dec to a String and change dec=rew.nextInt(); to dec=rew.nextLine(); then it will work fine. Here is a complete example that you can copy and paste into a blank file to see that it works correctly:
import java.util.*;
public class Program
{
public static Scanner rew = new Scanner(System.in);
public static void main(String[] args) {
String dec;
do {
System.out.println("Input info:");
String name = stringGetter("Name: ");
String yearandsec = stringGetter("Year and section: ");
dec = stringGetter("Enter 1 to continue: ");
} while(dec.equals("1"));
}
public static String stringGetter(String ny){
System.out.println(ny);
return rew.nextLine();
}
}
You may also want to consider adding proper parsing and validation to your program. Currently your program will behave in an undesirable way if the user enters invalid data.
The line:
dec = rew.nextInt();
Is reading an int value from the input stream and is not processing the newline character, then when you come back to point where you get the name at which point a new line is still in the Reader's buffer and gets consumed by the stringGetter returning an empty value for name.
Change the line to do something like:
do {
//....
s = stringGetter("Another (y/n)? ");
} while ("y".equals(s));
Well you haven't told us what "rew" is, nor what rew.nextInt() does. Is it possible that rew.nextInt() is waiting for the user to hit return, but only actually consuming one character of the input - so that the next call to rew.nextLine() (for the name) just immediately takes the rest of that line? I suspect that's what's happening because you're using System.in - usually reading from System.in only gives any input when you hit return.
(It's possible that this is also only a problem on Windows - I wonder whether it consumes the "\r" from System.in as the delimiter, leaving "\n" still in the buffer. Not sure.)
To test this, try typing in "1 Jon" when you're being asked whether or not to continue - I think it will then use "Jon" as the next name.
Essentially, I think using Scanner.nextInt() is going to have issues when the next call is to Scanner.nextString(). You might be better off using a BufferedReader and calling readLine() repeatedly, then parsing the data yourself.