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How to format an output?

(In Java) Write a program that accepts names and formats them as follows: If the input is:
John Anthony Brown
Then the output must be:
Brown, John A.
Here is what I have
int mn;
String input3;
int fn;
int ln;
String firstName;
String lastName;
String middleName;
Scanner scnr = new Scanner(System.in);
String input = scnr.nextLine();
fn = input.indexOf(" ");
firstName = input.substring(0, fn);
middleName = input.substring(fn+1, input.length());
mn = middleName.indexOf(" ");
lastName = input.substring(mn+1, input.length());
System.out.println(lastName + ", " + mn + " " + firstName + ".");
}
I keep trying different things and get weird outputs such as "ry A Lee, 1 Mary." for the input "Marry A Lee"
This topic was never covered in my class and I am very confused.

Because this is homework, I’ll give code fragments:
Firstly, use split() to break up the text into words:
String[] names = input.split(" ");
Then build up your result:
String result = names[2] + ", " + names[0] + ", " + names[1].charAt(0) + ".";
There are more elegant ways of doing it, but this way is arguably the easiest to understand.
You could get fancier by catering for varying numbers of names.

Try something like this:
String[] items = input.split(" ");
//if there are three item in items, then it is the pattern you mentioned
if (items.length == 3) {
System.out.println(items[2] + "," + items[0] + items[1].charAt(0) + ".");
}

Problems with Output in Java

I have no idea why my output is not coming out correct. For example, if the input is "Running is fun" then the output should read "Is running fun". However, the output I am getting is "Iunning".
import java.util.Scanner;
public class Problem1 {
public static void main( String [] args ) {
Scanner sc = new Scanner(System.in);
System.out.println("Enter text: ");
String sentence = sc.nextLine();
int space = sentence.indexOf(" ");
String firstWord = sentence.substring(0, space + 1);
String removedWord = sentence.replaceFirst(firstWord, "");
String newSentence = removedWord.substring(0,1).toUpperCase() +
firstWord.substring(1).toLowerCase();
System.out.println("");
System.out.println( newSentence );
}
}

removedWord.substring(0,1).toUpperCase() this line adds the capitalized first letter of the second word in the sentence. (I)
firstWord.substring(1).toLowerCase(); adds every letter of the first word to the end of the sentence. (unning)
Thus this creates the output of Iunning. You need to add the rest of removedWord to the String, as well as a space, and the first letter of firstWord, as a lower case letter at the space in removedWord. You can do this more by using indexOf to find the space, and then using substring() to add on firstWord.toLowerCase() right after the index of the space:
removedWord = removedWord.substring(0, removedWord.indexOf(" ")) + " " +
firstWord.toLowerCase() +
removedWord.substring(removedWord.indexOf(" ") + 1,
removedWord.length());
String newSentence = removedWord.substring(0,1).toUpperCase() +
removedWord.substring(1, removedWord.length());
Output:
Is running fun

Your problem is that
firstWord.substring(1).toLowerCase()
Is not working as you expect it to work.
Given firstWord is “Running“ as in your example, then
”Running“.substring(1)
Returns ”unning“
”unning“.toLowerCase()
Obviously returns ”unning“

The problem is at String newSentence. You not make the right combination of firstWord and removedWord.
This is how should be for your case:
String newSentence = removedWord.substring(0, 1).toUpperCase() // I
+ removedWord.substring(1,2) + " " // s
+ firstWord.toLowerCase().trim() + " " // running
+ removedWord.substring(2).trim(); // fun
EDIT(add new solution. credits #andy):
String[] words = sentence.split(" ");
words[1] = words[1].substring(0, 1).toUpperCase() + words[1].substring(1);
String newSentence = words[1] + " "
+ words[0].toLowerCase() + " "
+ words[2].toLowerCase();

This works properly:
public static void main(String[] args) {
Scanner sc = new Scanner(System.in);
System.out.println("Enter text: ");
String sentence = sc.nextLine();
int space1 = sentence.indexOf(' ');
int space2 = sentence.indexOf(' ', space1 + 1);
if (space1 != -1 && space2 != -1) {
String firstWord = sentence.substring(0, space1 + 1);
String secondWord = sentence.substring(space1 + 1, space2 + 1);
StringBuilder newSentence = new StringBuilder(sentence);
newSentence.replace(0, secondWord.length(), secondWord);
newSentence.replace(secondWord.length(), secondWord.length()+ firstWord.length(), firstWord);
newSentence.setCharAt(0, Character.toUpperCase(newSentence.charAt(0)));
newSentence.setCharAt(secondWord.length(), Character.toLowerCase(newSentence.charAt(secondWord.length())));
System.out.println(newSentence);
}
}

Name Reversing in strings

Write a method lastNameFirst that takes a string containing a name such as "Harry Smith" or "Mary Jane Lee", and that returns the string with the last name first, such as "Smith, Harry" or "Lee, Mary Jane".
im supposed to check it against
http://wiley.code-check.org/codecheck/files?repo=bjlo2&problem=05_02
i post this
String firstName = name.substring(0, name.indexOf(" "));
String lastName = name.substring(name.indexOf(" "));
String cName = lastName + ", " + firstName;
if ( lastName == " " )
{
cName = firstName;
}
return cName;
I get 0/4 everytime please help im completely lost.

It might be simpler to create an array using the split function of the String class, then join them:
String cName = String.join(", ", Collections.reverse(Arrays.asList(name.split(" "))));
String.join is only in Java 8 I believe, if you're not using 8 you can use something like the following:
String[] names = name.split(" ");
String cName = names[1] + ", " + names[0];
You should also be using the equals method for comparing String and other objects:
String[] names = name.split(" ");
String cName = names[1].equals(" ") ? names[0] : names[1] + ", " + names[0];

Please try this code
String first = name.substring(name.lastIndexOf(" "));
String last = name.substring(0, name.lastIndexOf(" "));
String result = first + "," + last;

Your solution is very close. Here's 2 hints to get to the right solution:
What separates the first and last name is the last, not the first space (consider using str.lastIndexOf(" ")).
As mentioned in the comments, when comparing strings, you can't use str1 == str2, you have to use str1.equals(str2)

You only need the last space in your name, which you can get with String.lastIndexOf(int). Then you test if that is less then 0, if so return the input name. Otherwise, concatenate and return your name in the desired format. Using a ternary (or conditional operator ? :) that might look something like,
int p = name.lastIndexOf(' ');
return (p < 0) ? name : name.substring(p + 1) + ", " + name.substring(0, p);

I put this for that Question and it passed all 4 tests they had.
public static String lastNameFirst(String name)
{
String LastToFirst = "";
if(!name.contains(" ")){
return name;
}
int index = name.indexOf(" ");
int secondIndex = name.indexOf(" ", index + 1);
// exclusive of last index
if(secondIndex != -1) {
LastToFirst += name.substring(secondIndex+1,name.length())+", ";
LastToFirst += name.substring(0,secondIndex);
}
else {
LastToFirst += name.substring(index +1,name.length()) + ", ";
LastToFirst += name.substring(0, index);
return LastToFirst;
}
A better solution for this would be to use an array, and store the characters in there and for the spacing one should add an index variable for where you want the splitting to happen- the string of interest. The solutions above do a good example of expalining this better, they consider cases where it is not a white space, but other symbols making the method more robust. Hope this helps.

I tried this code and all the four arguement works. Hope this helps!!
{
String[] names = name.split(" ");
String cName = "";
if(names.length > 2){
cName = names[2].equals(" ") ? names[0] : names[2] + ", " + names[0] + " " + names[1];
}
else if(names.length == 1){
cName = names[0]
}
else{
cName = names[1].equals(" ") ? names[0] : names[1] + ", " + names[0];
}
return cName;
}
}

public class Names
{
/**
Changes a name so that the last name comes first.
#param name a name such as "Mary Jane Lee"
#return the reversed name, such as "Lee, Mary Jane".
If name has no spaces, it is returned without change.
*/
public static String lastNameFirst(String name)
{
String result = "";
if(!name.contains(" "))
{
String firstOnly = name.substring(0);
return firstOnly;
}
else
{
String first = name.substring(name.lastIndexOf(" ")+1);
String last = name.substring(0, name.lastIndexOf(" "));
result = first + ", " + last;
return result;
}
}
}
This is the correct answer that will get you 4/4.

What's Wrong? Number Of Words In a Sentence Java

int numOfWords = str.length() - str.replace(" ", "").length();
Why does that not work? If str is equal to "Hello bye", numOfWords should equal 2, but when ran numOfWords equals 0. Any help would be greatly appreciated!

You are only replacing one blank, so the output will be 1 (at least this is what is produce in my JVM)
If you want to know the number of words then either add 1 to this number or use
str.split(" ").length;

Why dont you use :
int numOfWords = str.split(" ").length;

I hope out put is much clear
public static void main(String[] args) {
String str = "Hello bye";
System.out.println("Length of Input String = " + str.length() + " for String = " + str);
System.out.println("Length of Input String with space removed = " + str.replace(" ", "").length() + " for String = "
+ str.replace(" ", ""));
int numOfWords = str.length() - str.replace(" ", "").length();
System.out.println(numOfWords);
}
Output
Length of Input String = 9 for String = Hello bye
Length of Input String with space removed = 8 for String = Hellobye
1

Array issue out of bounds [closed]

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I have tried so many variations of this code and I can't seem to get it correct.
I get an array out of bounds issue for the second if statement if I try something only with two parts. However, it works fine if there are 3 parts in the name.
import java.util.Scanner;
public class testArray
{
public static void main(String[]args)
{
Scanner input = new Scanner(System.in);
String fullName = input.nextLine();
fullName = fullName + " " + " ";
System.out.println(fullName);
String [] parts = fullName.split(" ");
String firstName = parts[0];
String middleName = parts[1];
String lastName = parts[2];
String firstNameInitial = firstName.substring(0,1).toUpperCase(); //capitalizes first initial
String middleNameInitial = middleName.substring(0,1).toUpperCase(); //capitalizes second initial
String lastNameInitial = lastName.substring(0,1).toUpperCase(); //capitalizes third initial
String initials = firstNameInitial + middleNameInitial + lastNameInitial; //Combines initials of name in capital form
if (parts.length == 3)
{
System.out.println(initials);
System.out.println(lastName.toUpperCase() + ", " + firstNameInitial+firstName.substring(1,parts[0].length()) + " " + lastNameInitial + ".");
System.out.println(lastNameInitial + lastName.substring(1,parts[2].length()) + ", " + firstNameInitial+firstName.substring(1,parts[0].length()) + " " + middleNameInitial + middleName.substring(1,parts[1].length()));
}
if (parts.length == 2)
{
System.out.println("error");
}
}
}

That's because the way you initialize your variables:
String firstName = parts[0];
String middleName = parts[1];
String lastName = parts[2];
Here, if parts only has index 0 and 1 (a length of 2) you will get an exception because there is no parts[2] (it's index is out of bounds).
Modify that to something like this:
String firstName = parts[0];
String middleName = null;
String lastName = parts[1];
if (parts.length > 2) {
middleName = parts[1];
lastName = parts[2];
}
With this code, middleName will only be set if parts has a length greater than 2, which means that the index 2 will exist. Otherwise, middleName will be null (or you could change this to be an empty string or whatever you would like)

You are trying to access the 3rd object in the array before you check how long the array is.
try this instead:
import java.util.Scanner;
public class testArray
{
public static void main(String[]args)
{
Scanner input = new Scanner(System.in);
String fullName = input.nextLine();
fullName = fullName + " " + " ";
System.out.println(fullName);
String [] parts = fullName.split(" ");
if(parts.length == 3)
{
String firstName = parts[0];
String middleName = parts[1];
String lastName = parts[2];
String firstNameInitial = firstName.substring(0,1).toUpperCase(); //capitalizes first initial
String middleNameInitial = middleName.substring(0,1).toUpperCase(); //capitalizes second initial
String lastNameInitial = lastName.substring(0,1).toUpperCase(); //capitalizes third initial
String initials = firstNameInitial + middleNameInitial + lastNameInitial; //Combines initials of name in capital form
System.out.println(initials);
System.out.println(lastName.toUpperCase() + ", " + firstNameInitial+firstName.substring(1,parts[0].length()) + " " + lastNameInitial + ".");
System.out.println(lastNameInitial + lastName.substring(1,parts[2].length()) + ", " + firstNameInitial+firstName.substring(1,parts[0].length()) + " " + middleNameInitial + middleName.substring(1,parts[1].length()));
}else{
System.out.println("error");
}
}
}

i think these line you want to put just after calling split:
String [] parts = fullName.split(" ");
if (parts.length == 2)
{
System.out.println("error");
return;
}
so the code would look like:
public static void main(String[]args) {
Scanner input = new Scanner(System.in);
String fullName = input.nextLine();
fullName = fullName + " " + " ";
System.out.println(fullName);
String [] parts = fullName.split(" ");
if (parts.length == 2)
{
System.out.println("error");
} else if(parts.length == 3) {
String firstName = parts[0];
String middleName = parts[1];
String lastName = parts[2];
String firstNameInitial = firstName.substring(0,1).toUpperCase(); //capitalizes first initial
String middleNameInitial = middleName.substring(0,1).toUpperCase(); //capitalizes second initial
String lastNameInitial = lastName.substring(0,1).toUpperCase(); //capitalizes third initial
String initials = firstNameInitial + middleNameInitial + lastNameInitial; //Combines initials of name in capital form
System.out.println(initials);
System.out.println(lastName.toUpperCase() + ", " + firstNameInitial+firstName.substring(1,parts[0].length()) + " " + lastNameInitial + ".");
System.out.println(lastNameInitial + lastName.substring(1,parts[2].length()) + ", " + firstNameInitial+firstName.substring(1,parts[0].length()) + " " + middleNameInitial + middleName.substring(1,parts[1].length()));
}
}

i might suggest splitting on white space rather that " "
so for example
String [] parts = fullName.split("\\s+");
also why are you adding spaces (fullName = fullName + " " + " ";)
also you might not get to your parts comparison because you will hit the String extraction from the array first, put your if check (if(parts.length == 3)) straight after the splitting (String [] parts = fullName.split("\\s+");)

The error comes from here:
Scanner input = new Scanner(System.in);
String fullName = input.nextLine();
fullName = fullName + " " + " ";
System.out.println(fullName);
String [] parts = fullName.split(" ");
String firstName = parts[0];
String middleName = parts[1];
String lastName = parts[2];
If someone enters text that is less than 3 words long, you get an ArrayIndexOutOfBoundsException. You have to add something like:
Scanner input = new Scanner(System.in);
String [] parts = null;
while (input.hasNext()) {
System.out.println("Please enter first middle and last name");
String fullName = input.nextLine();
fullName = fullName + " " + " ";
System.out.println(fullName);
parts = fullName.split(" ");
if (parts.length == 3)
break;
}
String firstName = parts[0];
String middleName = parts[1];
String lastName = parts[2];
Which will prompt the user for three words until you get the right amount.

Issue is here
String middleName = parts[1];
String lastName = parts[2];
You are appending two white spaces for fullName fullName = fullName + " " + " "; but actually these spaces won't append as there is no text after fullName, hence parts consists only one element at 0 position. and you are calling 1st position of parts array which is not available String middleName = parts[1]; So you are seeing ArrayIndexOutOfBoundsException

0,1,2,3,4 >> these are indexed till 4 but the total components or length is 5 .
So In
firstName.substring(1,parts[0].length())
Here, "parts[0].length()" should be replaced by "parts[0].length()-1" because the previous is increasing the size by 1 and hence array is out of bound..
The same error u will get in next line.
So replace every .length with .length-1 ..
And remove this line
fullName = fullName + " " + " "; because it increases the length of variable path to 5 and hence it dosent goes in the if statements