The problem requires to input different values for each attribute.Ex:
Color Black White
Water Cool Hot Medium
Wind Strong Weak
I made ArrayList of ArrayList of String to store such thing as no. of values of each attribute is not fixed.The user inputs Black White and on hitting new line the program has to start taking values of NEXT attribute( Cool Hot Medium).The no. of attributes has been already specified.I followed some (almost related) answers here and wrote the following code:
ArrayList<ArrayList<String>> attributes = new ArrayList<ArrayList<String>>();
String input;
for(i=0; i<num_of_Attributes ;i++)
{ System.out.print(" Enter attribute no." + i+1 + " : ");
ArrayList<String> list = new ArrayList<String>();
while(! input.equals("\n"))
{
list.add(input);
input = sc.nextLine();
}
attributes.add(list);
}
The program prints "Enter Attribute 1 : " but even after new line it doesn't print "Enter attribute 2 : ".It goes into infinite loop. How can I achieve what the program requires to do? sc is my Scanner object.
You should read:
http://docs.oracle.com/javase/7/docs/api/java/util/Scanner.html#nextLine%28%29
specifically the part that states:
This method returns the rest of the current line, excluding any line separator at the end
So, if the user inputs an empty line with only the line separator \n, you will read an empty line without such line separator.
Check while (!input.isEmpty()) or, even better, while (!input.trim().isEmpty())
As a more general rule, you can debug your program (or even just print input) to try to find out yourself what is the actual value you are checking.
As a quick-Hack you can do sth. like
for (i = 0; i < num_of_Attributes; i++) {
input = " ";
System.out.print(" Enter attribute no." + (i + 1) + " : ");
ArrayList<String> list = new ArrayList<String>();
while (!input.isEmpty()) {
list.add(input);
input = sc.readLine();
}
attributes.add(list);
}
not nice but it works. Please also watch out for calculating in String concaternation. In you code it will print 01, 11, 21 and so on. With brackets it will work.
Related
How do I print only the first letter of the first word and the whole word of the last? for example,
I will request username input like "Enter your first and last name" and then if I type my name like "Peter Griffin", I want to print only "P and Griffin". I hope this question make sense. Please, help. I'm a complete beginner as you can tell.
Here is my code:
public static void main(String[] args) {
Scanner scan=new Scanner(System.in);
System.out.println("Enter your first and last name");
String fname=scan.next();
}
The String methods trim, substring, indexof, lastindexof, and maybe split should get you going.
This should do the work (typed directly here, so syntax errors might be there)
String fname=scan.nextLine(); // or however you would read whole line
String parts=fname.split(" ");
System.out.printf("%s %s",parts[0].substring(0,1),parts[parts.length-1]);
What you have to do next:
Check if there actually at least 2 elements in parts array
Check if first element is actually at least 1 char (no empty parts)
Check if there is actually line to read
Do your next homework yourself, otherwise you will not anything
I recommand you to watch subString(1, x) and indexOf(" ") to cut from index 1 to first space.
or here a other exemple, dealing with lower and multi name :
String s = "peter griffin foobar";
String[] splitted = s.toLowerCase().split(" ");
StringBuilder results = new StringBuilder();
results.append(String.valueOf(splitted[0].charAt(0)).toUpperCase() + " ");
for (int i = 1; i < splitted.length; i++) {
results.append(splitted[i].substring(0, 1).toUpperCase() + splitted[i].substring(1)+" ");
}
System.out.println(results.toString());
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.
I'm trying to make a program to just derive a user-entered polynomial. I'm trying to account for things like "3x2 + 5x4 + 3" instead of just "3x2+5x4+3". I currently have the delimiter setup as scan.useDelimiter("[A-Za-z\\s+-]");. I thought this would cover any letter, the + or - symbols, as well as ANY number of whitespace characters? But when I put the input as something like "3x2 + 5x4 + 3" the scanner just stops at that point when I'm using scan.nextInt().
I'll throw in the relevant parts of the code that I'm using to test stuff out. I'm sure there's much more efficient routes(maybe a HashMap, and removing the constant from the list, etc) but I'll worry about that after I get something like this figured out!
ArrayList<Integer> coeffArr = new ArrayList<>();
ArrayList<Integer> expArr = new ArrayList<>();
String polynomial;
Scanner scan = new Scanner(System.in);
System.out.println("Write your polynomial in the form of (coefficient)(variable)(exponent). (ie: 3x2 is 3x squared):");
polynomial = scan.nextLine();
scan = new Scanner(polynomial);
scan.useDelimiter("[A-Za-z\\s+-]");
while(scan.hasNextInt())
{
coeffArr.add(scan.nextInt());
if(scan.hasNextInt())
expArr.add(scan.nextInt());
}
if(coeffArr.size() != expArr.size())
constant = coeffArr.get(coeffArr.size()-1);
for(int i = 0; i < expArr.size(); i++)
{
System.out.print( (coeffArr.get(i) * expArr.get(i)) + "x" + (expArr.get(i)-1) + " ");
}
So essentially, if I put the input as "3x3+5x2+4" it will output "9x2 + 10x1", but if I were to do "3x3 + 5x2 + 4" all I'll get in the output is "9x2". How do I fix that and why does it happen?
I am taking user input using scanner and want to store 2 argument given from command line how ever I am only able to get one.
Also I believe hasNextInt() returns boolean value if there is a nextInt, however when I enter a non-int value it doesnot break the loop.
I have checked sources online and on stackoverflow before posting this questions but did not get what I was looking for.
Scanner s = new Scanner(System.in);
int first = 0;
int second = 0;
System.out.println("Please enter number: ");
s.useDelimiter(",");
while (s.hasNextInt()) {
first = s.nextInt();
System.out.print("firstArgument: " + first + "\n");
second = s.nextInt();
System.out.print("secondArgument: " + second + "\n");
}
The problem is that your code calls s.hasNextInt() for every odd-numbered input, but it tries to take each even-numbered input without performing a check. Therefore, it requires inputs like this:
1,2,3,4,5,6,done
1,2,3,4,done
1,2,done
However, inputs like this would result in an exception:
1,2,3,4,5,done
1,2,3,done
1,done
Note that a non-numeric input must appear after a comma on the same line.
To fix this problem, add a check before reading the second value:
while (s.hasNextInt()) {
first = s.nextInt();
if (!s.hasNextInt()) break'
second = s.nextInt();
System.out.print("firstArgument: " + first + "\n");
System.out.print("secondArgument: " + second + "\n");
}
If you would like to allow other characters, such as end-of-line markers, to end your comma-separated list, use a different expression for delimiters:
s.useDelimiter("[,\n]");
For a uni assignment, I have to take input from a text file and sort it into two separate arrays. The text file is a football league table, arranged as such:
Barcelona 34
Real Madrid 32
I have written a piece of code like this:
holdingString = fileInput.readLine ();
StringTokenizer sort = new StringTokenizer (holdingString + " ");
countOfTokens = sort.countTokens();
System.out.println (countOfTokens + " tokens: " + holdingString);
This prints out the number of tokens and what the tokens are for each line, so it gives output of
Two tokens: Barcelona 34
Three tokens: Real Madrid 32
I've then written this piece of code:
for (int i = 0; i < countOfTokens; i++)
{
String temp = sort.nextToken ();
System.out.println(temp);
}
This reads just the next token and prints it out.
However, rather than printing the next token out, I want to check if it is a word or a number, and separate it into a different array accordingly, so it will be like this:
ArrayTeam Zero Element Barcelona
ArrayTeam First Element Real Madrid
ArrayPoints Zero Element 34
ArrayPoints First Element 32
What's the easiest way to do this? I've tried using a try/catch, but didn't get it right. I've also tried using an if statement with \d, but that's not worked either.
Like AmitD, I agree that using split is more appropriate in this case, but if you still like to use a StringTokenizer you do something like:
StringBuilder teamName=new StringBuilder();
for (int i = 0; i < countOfTokens-1; i++)
{
if (i>0) teamName.append(' ');
teamName.append(sort.nextToken());
}
teamNames[k]=teamName.toString(); //add the new team to your teamNames array
points[k]=Integer.parseInt(sort.nextToken()); //if your points array is of int type
you could use java.util.Scanner class to read data from the file. it has methods such as nextInt(), nextDouble ...whhich might be useful in your case.
Scanner scan = new Scanner(file);
int number;
if(scan.hasNextInt()){
number = scan.nextInt();
}
check Scanner API
String readLine = "Real Madrib 40";
String[] team = readLine.split( "\\d" );
System.out.println(team[0]);
String score = readLine.replace( team[0],"" );
System.out.println(score);
Output :
team[0] : Real Madrib
score : 40
You can save all that trouble using split
String strs[] = holdingString.split("\\s");
E.g.
"Barcelona 34".split("\\s"); will return you Array of Strings where
array[0]=Barcelona array[1]=34
From Javadoc of StringTokenizer
StringTokenizer is a legacy class that is retained for compatibility reasons although its use is discouraged in new code. It is recommended that anyone seeking this functionality use the split method of String or the java.util.regex package instead.
Update
As #madhairsilence pointed out
You need another deliminator. You can use = like property files
"Real Madrid =34".split("=");//will return you Array of Strings where
array[0]=Real Madrid, array[1]=34
You can use Scanner as you are reading from file.