Develop Reference

How can I obtain the first character of a string that is given by a user input in java

I want the user to input a String, lets say his or her name. The name can be Jessica or Steve. I want the program to recognize the string but only output the first three letters. It can really be any number of letters I decide I want to output (in this case 3), and yes, I have tried
charAt();
However, I do not want to hard code a string in the program, I want a user input. So it throws me an error. The code below is what I have.
public static void main(String args[]){
Scanner Name = new Scanner(System.in);
System.out.print("Insert Name here ");
System.out.print(Name.nextLine());
System.out.println();
for(int i=0; i<=2; i++){
System.out.println(Name.next(i));
}
}
the error occurs at
System.out.println(Name.next(i)); it underlines the .next area and it gives me an error that states,
"The Method next(String) in the type Scanner is not applicable for arguments (int)"
Now I know my output is supposed to be a of a string type for every iteration it should be a int, such that 0 is the first index of the string 1 should be the second and 2 should be the third index, but its a char creating a string and I get confused.

System.out.println("Enter string");
Scanner name = new Scanner(System.in);
String str= name.next();
System.out.println("Enter number of chars to be displayed");
Scanner chars = new Scanner(System.in);
int a = chars.nextInt();
System.out.println(str.substring(0, Math.min(str.length(), a)));

The char type has been essentially broken since Java 2, and legacy since Java 5. As a 16-bit value, char is physically incapable of representing most characters.
Instead, use code point integer numbers to work with individual characters.
Call String#codePoints to get an IntStream of the code point for each character.
Truncate the stream by calling limit while passing the number of characters you want.
Build a new String with resulting text by passing references to methods found on the StringBuilder class.
int limit = 3 ; // How many characters to pull from each name.
String output =
"Jessica"
.codePoints()
.limit( limit )
.collect(
StringBuilder::new,
StringBuilder::appendCodePoint,
StringBuilder::append
)
.toString()
;
Jes

When you take entry from a User it's always a good idea to validate the input to ensure it will meet the rules of your code so as not to initiate Exceptions (errors). If the entry by the User is found to be invalid then provide the opportunity for the User to enter a correct response, for example:
Scanner userInput = new Scanner(System.in);
String name = "";
// Prompt loop....
while (name.isEmpty()) {
System.out.print("Please enter Name here: --> ");
/* Get the name entry from User and trim the entry
of any possible leading or triling whitespaces. */
name = userInput.nextLine().trim();
/* Validate Entry...
If the entry is blank, just one or more whitespaces,
or is less than 3 characters in length then inform
the User of an invalid entry an to try again. */
if (name.isEmpty() || name.length() < 3) {
System.out.println("Invalid Entry (" + name + ")!\n"
+ "Name must be at least 3 characters in length!\n"
+ "Try Again...\n");
name = "";
}
}
/* If we get to this point then the entry meets our
validation rules. Now we get the first three
characters from the input name and display it. */
String shortName = name.substring(0, 3);
System.out.println();
System.out.println("Name supplied: --> " + name);
System.out.println("Short Name: --> " + shortName);
As you can see in the code above the String#substring() method is used to get the first three characters of the string (name) entered by the User.

How to find strings within a text file in JAVA

I'd like to just see an example with some explanation.
What string functions do I use to compare the objects and does it compare each character or the actual word without any additional letters to it?
Thanks

I tried doing something very similar to this question for a project awhile ago. There are numerous ways to do this in Java, but I used the Scanner class and the File class.
public static void main(String[] args)
{
Scanner input = new Scanner(System.in); //Just a normal scanner
System.out.println("Please enter in the pathname to the file you want to view.");
String pathname = input.nextLine(); //Pathname to text file
File book = new File(pathname); //Creating a new file using the pathname
if(book.canRead() == false) //If Java cant read the file, this will pop up
{
System.out.println("Your file cannot be read");
}
else if(book.canRead() == true) //If Java can read the file, then this asks for the word to search for
{
System.out.println("Please enter in the word you wish to search for.");
wordToSearchFor = input.nextLine();
wordCounter(book); //Calls the method
}
System.out.println(wordToSearchFor.toLowerCase() + " appeared " + numOfOccurrences + " times in " + pathname);
}
This is the main method where you use the File class to create a file based off of a pathname that you give it EX - C:\Users\alex\Downloads\mobydick.txt
I then check to see if you can read the file, and if you can, then I call a method to analyze the book itself
import java.io.*;
import java.util.Scanner;
public class TextReader
{
private static int numOfOccurrences; //Counter to keep track of the number of occurances
private static String wordToSearchFor; //String field so both methods can access it
/*
* This method takes in the file of the book so the scanner can look at it
* and then does all of the calculating to see if the desired word appears,
* and how many times it does appear if it does appear
*/
public static void wordCounter(File bookInput)
{
try
{
Scanner bookAnalyzer = new Scanner(bookInput); //Scanner for the book
while(bookAnalyzer.hasNext()) //While the scanner has something to look at next
{
String wordInLine = bookAnalyzer.next(); //Create a string for the next word
wordInLine = wordInLine.toLowerCase(); //Make it lowercase
String wordToSearchForLowerCase = wordToSearchFor.toLowerCase();
String wordToSearchForLowerCasePeriod = wordToSearchForLowerCase + ".";
if(wordInLine.indexOf(wordToSearchForLowerCase) != -1 && wordInLine.length() == wordToSearchFor.length())
{
numOfOccurrences++;
}
else if(wordInLine.indexOf(wordToSearchForLowerCasePeriod) != -1 && wordInLine.length() == wordToSearchForLowerCasePeriod.length())
{
numOfOccurrences++;
}
}
}
catch(FileNotFoundException e) //Self explanitory
{
System.out.println("The error is FileNotFoundException - " + e);
System.out.println("This should be impossible to get to because error checking is done before this step.");
}
}
Scanners in Java can be take a File object to analyze, which is the fist thing I do in this method. I then use a while loop and ask the Scanner if there is a word that follows the current word. As long as there is a word, this will continue to run. I then create a String of the current word that the scanner is on to use as a reference to compare against. I then use a method that comes with the String class to make everything lowercase because uppercase and lowercase letters matter.
The first if statement in this method checks if the current word that the scanner has matches what you are searching for using the indexOf method from the String class, which takes some string and looks to see if it exists in another string. The if statement comparison also makes sure that the desired word length is the same as the word length in the book in case you are looking up "the" and it doesnt mark "then" as a word since it contains "the". The second if statement does the same thing, just with your desired word with a period at the end. If you wanted to go the extra mile, you could also check for exclamation points, question marks, commas, and so forth, but I decided to just check for periods.
Every time one of these if statements is correct, I increment a variable by one, and after the scanner runs out of words to search for, I print out the total number of times that certain word appears in a text file.

How to check if the first 2 letters in a sting are a specific value

Edit Thanks for the help guys got it working now.
So I had a question to do to ask a user for first name and last name which I have done no problem but then I thought it's be good to expand the program so that if someone entered a surname like McCabe it would print T McC instead of TM. I'm just not sure about how to compare the first two letters of the secondname string to see if they are "mc".
public class InitialsAlt {
public static void main(String [] args){
Scanner keyboardIn = new Scanner (System.in);
String firstname = new String();
System.out.print (" Enter your first name ");
firstname = keyboardIn.nextLine();
String secondname = new String();
System.out.print (" Enter your second name ");
secondname = keyboardIn.nextLine();
if(secondname.charAt(0, 1)== "mc" ) {
System.out.print("Your initals are " + firstname.charAt(0)+ secondname.charAt(0,1,2));
}
else {
System.out.print("Your initals are " + firstname.charAt(0)+ secondname.charAt(0));
}
}
}

if (secondName.toLowerCase().startsWith("mc")) {

The easiest way is to use String.startsWith:
yourString.toLowerCase().startsWith("mc")
If you want to avoid lowercasing the entire string or creating a new object, only to check the first two characters:
yourString.length() >= 2
&& Character.toLowerCase(yourString.charAt(0)) == 'm'
&& Character.toLowerCase(yourString.charAt(1)) == 'c'
However, I would use the former solution as it is far more readable, and the performance hit from lowercasing the entire string is almost certainly negligible, unless you are doing this on quite large strings.

Use yourString.toLowerCase().indexOf("mc")==0. This will involve creation of a new String only once (Since indexOf() doesn't create a new one, using indexOf() would be better than using subString() here)

Use substring to get the first two letters, then convert to lowercase, then check to see if it equals:
String someString = "McElroy";
if (someString.subString(0,2).toLowerCase().equals("mc")) {
//do something
}

If its case insensitive you could use the Apache Commons Lang library:
if(StringUtils.startsWithIgnoreCase(secondname, "mc") {
// Do nice stuff
}
Otherwise, you can use:
if(StringUtils.startsWith(secondname.toLowerCase(), "mc") {
// Do nice stuff
}

New to string so how to manage this title applier

After reading the string methods description in a chapter i was trying to solve this programming exercise. here it is.
Write a program that asks for the user's name and then writes that name to the monitor with either "Ms." or "Mr." in front, depending if the name is for a female or male. Assume that the only female names are
Amy
Buffy
Cathy
and that the only male names are
Elroy
Fred
Graham
All other names will be echoed without a title. The program continues looping until the user hits "enter" without first typing a name.
C:\>java Title
Enter a name:
Amy Johnson
Ms. Amy Johnson
Enter a name:
Fred Smith
Mr. Fred Smith
Enter a name:
Zoltan Jones
Zoltan Jones
Enter a name:
C:\>
here is my code i know its wrong because i am very confused.
import java.util.Scanner;
class titleApplier {
public static void main(String[] args) {
String name;
String male = {"Elroy" , "Fred " , " Graham"};
String females = {"Amy", "Buffy", "Cathy"};
Scanner scan = new Scanner(System.in);
while(name.hasNext()) {
System.out.println("Enter a name ");
name = scan.nextLine();
if(name.equals(male)) {
System.out.println("Mr " + male);
}
else if (name.equals(females)) {
System.out.println(" Mrs " + females);
}
else {
System.out.println(scan.nextLine());
}
}
}
}

You're mostly on the right track, good work!
Instead of storing the names in Strings individually, you could just reference them directly in your if statements as such:
if(name.equals("Elroy") || name.equals("Fred") || name.equals("Graham")) {
System.out.println("Mr " + male);
}
Also, since you're providing first and last names, I don't think you should be matching with the equals method, but instead, checking to see if the name contains one of the names:
if (name.contains("firstName"))
As this looks like homework, try something along the same lines for the women yourself. Let me know if you have anymore questions. Good luck!

There are plenty of errors in your program which need to be corrected.Better give this a try.I have used BufferedReader since the Scanner class causes some problems while taking several input values within a loop.:-
import java.io.*;
import java.util.*;
class MF{
static boolean search(String arr[],String st){
for(int i=0;i<arr.length;i++){
if(arr[i].equalsIgnoreCase(st)==true)
return true;
}
return false;
}
public static void main(String args[])throws IOException{
String male[]={"Elroy","Fred","Graham"};
String fem[]={"Amy","Buffy","Cathy"};
BufferedReader br=new BufferedReader(new InputStreamReader(System.in));
while(true){
System.out.println("Enter name:-");
String st=br.readLine();
if(st.equals("")==false){
StringTokenizer str=new StringTokenizer(st);
String tok=str.nextToken();
if(search(male,tok)==true)
System.out.println("Mr."+st);
if(search(fem,tok)==true)
System.out.println("Ms."+st);
}
else
break;
}
System.out.println("Program terminates.");
}
}

A few observations from your code:
male and females should be arrays of String, not just a single String. (i.e. String[] females = {"Amy", "Buffy", "Cathy"};
Watch out for leading and trailing white spaces. "Fred" and "Graham" will never pass a comparison unless you call the String.trim() method.
The method hasNext() is not defined in the String class; thus the compilation error. If you are writing this on an IDE such as Eclipse, read the errors you are getting and resolve them. Even for a beginner this should not be difficult at all.
Your program prompts the user AFTER the name is already entered. This might be easier if you enclose your code in a do/while rather than in a while loop. This is a matter of preference, or course. Also, normally you would want the user input to appear in the same line as the prompt, so use System.out.print() for the prompt instead of System.out.println().
When you are learning, you should always try your programs with very controlled inputs. In this case, you should have tried the program with a single male name and female name, and once you got that part working, then you should try expanding your solution to handle multiple names.
Your code allows to enter a LINE (words separated by space) rather than a String (array of characters with no white spaces). Therefore, you need to break that line into tokens (words) and examine either the first token (first name) or the second token (last name) and compare it to the names in the array. Otherwise, the equals() method will return false. This is because 'Elroy Smith' is not equal to 'Elroy'. You can do what I just explained, or use other String methods such as contains() or startsWith().
You should append the title to the entered name, and not the first name in your String array. Instead of outputting "Mrs. Amy", your program should output "Mrs. Amy Smith".
Your while() clause does not capture this requirement: "The program continutes looping until the user hits "enter" without first typing a name." This method will always return true even if the line has a length of zero. Instead, use the String entered and loop only if the length of the String entered is larger than zero.
To eliminate unnecessary processing, you can use a boolean variable to see if the name has been found, in order to break (exit loop) or continue (skip to next iteration).
This is one potential solution (might not be the most effective, but easy for you to follow):
public static void main(String[] args)
{
String name;
String[] males = {"Elroy", "Fred ", " Graham"};
String[] females = {"Amy", "Buffy", "Cathy"};
Scanner scan = null;
do
{
System.out.print("Enter a name: ");
scan = new Scanner(System.in);
name = scan.nextLine();
boolean found = false;
// Search all possible male names
for (String temp: males)
{
if (name.startsWith(temp))
{
System.out.println("Mr. " + name + "\n");
found = true;
break; // stop looping if found
}
}
if (found) { continue; } // skip the rest of the loop if name has been found
// Search all possible female names (only if name has not been found)
for (String temp: females)
{
if (name.startsWith(temp))
{
System.out.println("Ms. " + name + "\n");
found = true;
break;
}
}
if (name.length() > 0 && !found)
{
// A name was entered but it was never found
System.out.println("Unknown name entered.\n");
}
} while (name.length() > 0);
scan.close();
}
The output:
Enter a name: Fred Smith
Mr. Fred Smith
Enter a name: Buffy Vampire Slayer
Ms. Buffy Vampire Slayer
Enter a name: Cathy Doe
Ms. Cathy Doe
Enter a name:
Exiting program.

Checking string formats in Java?

having problems doing something for a class I'm taking, since I missed a class or two. (I know it's looked down on to 'do someone's homework,' but I'm not looking for that.)
The assignment is as follows:
Write a program to do the following:
Prompt for input of someone's first, middle, and last name as a single string (using any combination of upper and lowercase letters).
Check to make sure the name was entered in the correct format (3 names separated by spaces). If the input is not correct, continue to request the input again until the format is correct.
Capitalize only the first letters of each part of the name, and print out the revised name.
Print out the initials for that name.
Print out the name in the format of: Lastname, Firstname, MI.
The major problem I'm having is the second part of the assignment; I got the first part, and I'm fairly sure I can manage through the rest, after I get the second set up.
import java.util.*;
public class TestStrings
{
public static void main(String[] args)
{
Scanner key = new Scanner(System.in);
String name;
System.out.print("Enter your name as 'First Middle Last': ");
name = key.nextLine();
}
}
From what I've gathered, I need to use the string.split? I'm not sure how to go about this, though, since I need to check to make sure there are three spaces, that aren't just right next to each other or something, such as "John(three spaces)Doe". I assume it's going to be some kind of loop to check through the input for the name.
The catch 22, is that I can't use arrays, or StringTokenizer. I must use the substring method.
Any help would be appreciated. Thanks. :D

To point you in the right direction to find the first name(since you cant use arrays):
String firstName = input.substring(0, input.indexOf(" "));
This will get you a substring from the start to the first space. If you research the indexOf and substring methods you should be able to go from there.

Look at the matches method if you know how to use regex. If not think about indexOf and substring methods.
http://docs.oracle.com/javase/1.5.0/docs/api/java/lang/String.html

You can use the substring and the indexOf functions of String class to get what you need.
String#indexOf: Get's the position of a String inside a String.
String#substring: Get's a substring contained in a String.
String s = "Luiggi Mendoza J.";
String x;
while(s.indexOf(" ") > 0) {
x = s.substring(0, s.indexOf(" "));
System.out.println(x);
s = s.substring(s.indexOf(" ") + 1);
}
x = s;
System.out.println(x);
The program output will be:
Luiggi
Mendoza
J.

Use a while loop to continuously check whether user entered a string that consists of 3 parts which are seperated via a single space character ' ', then use split() function to verify 3 parts of string. By using substring() as demonstrated here you can get names seperately:
public static void main ( String [] args )
{
String name = "";
boolean ok = false;
Scanner key = new Scanner( System.in );
while ( !ok )
{
System.out.print( "Enter your name as 'First Middle Last': " );
name = key.nextLine();
try
{
if ( name.split( " " ).length == 3 )
ok = true;
}
catch ( Exception e ){ }
}
if ( ok )
{
String firstName = name.substring(0, name.indexOf(" "));
String middleName = name.substring(firstName.length()+1,
name.lastIndexOf(" "));
String surname = name.substring(middleName.length()+firstName.length()+2,
name.length());
}
}

This works using Pattern/Matcher and regexs. Also guards against strings of length 1 when adjusting case.
private static String properCase(String str) {
return str.substring(0, 1).toUpperCase()
+ (str.length() >= 1 ? str.substring(1).toLowerCase() : "");
}
public static void main(String[] args) {
boolean found = false;
do {
Scanner scanner = new Scanner(System.in);
System.out.print("Enter your name as 'First Middle Last': ");
Pattern p = Pattern.compile("\\s*(\\w+?)\\s(\\w+?)\\s(\\w+)+\\s*");
Matcher m = p.matcher(scanner.nextLine());
found = m.find();
if (found) {
String first = m.group(1);
String middle = m.group(2);
String last = m.group(3);
String revised = properCase(first) + " " + properCase(middle)
+ " " + properCase(last);
System.out.println(revised);
System.out
.printf("%s %s %s.\n", properCase(last),
properCase(first), middle.substring(0, 1)
.toUpperCase());
}
} while (!found);
}