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Want to print my stored names in array by JoptionPane, JAVA

public static void main(String[] args) {
i got to enter the amount of names i want, then input them by scanner in console, and after print the longest one, it's mostly done, but i want to print it by JoptionPane aswell
Scanner wczytanie = new Scanner(System.in);
System.out.println("ENTER THE AMOUNT OF NAMES");
int size = wczytanie.nextInt();
String[] array = new String[size];
System.out.println("ENTER THE NAMES");
String name = wczytanie.nextLine();
for (int i = 0; i < array.length; i++) {
array[i] = wczytanie.nextLine();
if (name.length() < array[i].length()) {
name = array[i];
}
}
// System.out.println("LONGEST NAME: " + name);
String name1 = new String();
if(name == name1) {
JOptionPane.showMessageDialog(null, " THE LONGEST NAME IS " + name1);
}
}

You have a lot of problems here: you're reading from the scanner before the loop when reading names and you're doing a raw object equality on a new string for some reason that will never work. You want something more like this:
public static void main(String[] args) {
try (Scanner scanner = new Scanner(System.in)) {
System.out.println("How many names? ");
int num = scanner.nextInt();
List<String> names = new ArrayList<>(num);
System.out.println("Enter names: ");
for (int i = 0; i < num; i++) {
names.add(scanner.next());
}
String longest = names.stream().reduce((a, b) -> a.length() > b.length() ? a : b).get();
System.out.println("The longest name is: " + longest);
JOptionPane.showMessageDialog(null, "The longest name is: " + longest);
}
}

while loop with store value for next while loop in java

I'm a beginner in Java. I have an assignment that require me to take 3 input from user, then output the 3 at the same time.
here is my code. i have only get 1 output.
suppose look like this:
anyone could help, thx!
here is my code
Scanner sc = new Scanner(System.in);
int i = 0;
String classname = " ";
String rating = " ";
int plus = 0;
while(i < 3){
System.out.print("What class are you rating? ");
classname = sc.nextLine();
System.out.print("How many plus signs does " + classname +" get? ");
rating = sc.nextLine();
plus = Integer.parseInt(rating);
i++;
}
System.out.print(classname + ": ");
while (plus > 0){
System.out.print("+");
plus --;
}
System.out.println();

The very first thing I would do is create a Course POJO (Plain Old Java Object). It should have two fields, name and rating. And I would implement the display logic with a toString in that Course POJO. Like,
public class Course {
private String name;
private int rating;
public Course(String name, int rating) {
this.name = name;
this.rating = rating;
}
public String toString() {
StringBuilder sb = new StringBuilder();
for (int i = 0; i < rating; i++) {
sb.append("+");
}
return String.format("%s: %s", name, sb);
}
}
Then your main method simply involves filling a single array of three Course instances in one loop, and displaying them in a second loop. Like,
Scanner sc = new Scanner(System.in);
Course[] courses = new Course[3];
int i = 0;
while (i < courses.length) {
System.out.print("What class are you rating? ");
String className = sc.nextLine();
System.out.printf("How many plus signs does %s get? ", className);
int classRating = Integer.parseInt(sc.nextLine());
courses[i] = new Course(className, classRating);
i++;
}
i = 0;
while (i < courses.length) {
System.out.println(courses[i]);
i++;
}

You overwrite your variables classname and rating in each loop. You need to store each iteration in a field of an array.
Scanner sc = new Scanner(System.in);
int i = 0;
String[] classname = new String[3]; //create array
String rating = " "; //rating can be overwritten, it is not needed after the loop
int[] plus = new int[3];
while(i < 3){
System.out.print("What class are you rating? ");
classname[i] = sc.nextLine(); //name[index] to read/write fields of an array
//index starts at 0
System.out.print("How many plus signs does " + classname +" get? ");
rating = sc.nextLine();
plus[i] = Integer.parseInt(rating);
i++;
}
for(i = 0;i<3;i++){ //iterate over all elements in the array
System.out.print(classname[i] + ": ");
while (plus[i] > 0){
System.out.print("+");
plus[i] --;
}
System.out.println();
}

Check if user entered both a first and last name

I'm making a program that gives random lottery numbers to inputted names. The problem though is that I have to make sure the user entered both a first and last name. I'm using a method of finding the space in the users input, then creating substrings from that data, but I keep on getting the error "incompatible type" right under my for loop. Any help would be greatly appreciated!
enter code here
import java.util.Scanner; //Import scanner class
import java.util.Random; //Import random number generator
import java.io.*; //Import PrintWriter
public class Lab4ZinkovskyFl //Program that lets user enter a name and generates random lottery numbers for that name
{
public static void main (String[] args) throws IOException
{
Scanner keyboard = new Scanner (System.in);
Random randomNumbers = new Random();
String again = "y"; //Control the loop
int r1 = randomNumbers.nextInt(100)+ 1; //*******************
int r2 = randomNumbers.nextInt(100)+ 1; //* Random lottery
int r3 = randomNumbers.nextInt(100)+ 1; //* numbers for
int r4 = randomNumbers.nextInt(100)+ 1; //* program
int r5 = randomNumbers.nextInt(100)+ 1; //*******************
while (again.equalsIgnoreCase ("y")) // Allows the user to continue the loop
{
System.out.println ("Please enter first and last name to enter the lottery.");
String fullName = keyboard.nextLine();
boolean space = false; // Checks for first and last name
for (int i = 0; i < fullName.length(); i++)
{
if (fullName.indexOf(i) == " ")
{
space = true;
spaceIndex = i;
}
else
{
System.out.println ("Error, please enter both first and last name to continue.");
}
}
String firstName = fullName.substring (0, spaceIndex);
String lastName = fullName.substring (spaceIndex, fullName.length());
System.out.println (lastName + ", " + firstName + ": " + r1 + ", " + r2 + ", " + r3 + ", " + r4 + ", " + r5);
System.out.println ("Run the lottery again? (y=yes)");
again = keyboard.nextLine();
}
}
}

You can split the user input by " ", like this:
String[] names = fullName.split(" ");
And then you create a method to return true if the user do enters the full name.
for (int i = 0 ; i < names.length ; i++) {
if (names[i].trim().equals("")) {
names[i] = null;
}
}
int elementsWithText = 0;
for (int i = 0 ; i < names.length ; i++) {
if (names[i] != null) {
elementsWithText++;
}
}
return elementsWithText == 2;
Something like that. Hopefully you figure what I am doing. If you don't know what the methods calls are doing, they are all from String. Here is the docs:
http://docs.oracle.com/javase/7/docs/api/java/lang/String.html

indexOf() takes in a char as input (in your case). Change i to " "(space)

You need to write like this
if (fullName.indexOf(" ") == -1)
{
System.out.println ("Error, please enter both first and last name to continue.");
}
else
{
space = true;
spaceIndex = i;
}
But why you choose for loop?
#sweeper has given the best solution.

i don't get the right answer, why?

I'm quite new to java, and I've just started the course for a few days. I wrote the following code to make a simple phone book. It gets names and phone numbers first, then it gets a name and passes the phone number. Except the first name, if I enter any name it will print the last line (the name is not in the list) then the related number!!! Why?
import java.util.Scanner;
class MyPhoneBook {
public static void main(String[] args) {
Scanner myScan = new Scanner(System.in);
String[] name = new String[200];
String[] number = new String[200];
System.out.println("when finished all contacts, just type : finish");
for (int a = 0; a < 200; a++) {
System.out.print("\nenter name:");
name[a] = myScan.nextLine();
if (name[a].equals("finish")) {
break;
} else {
}
System.out.print("enter number:");
number[a] = myScan.nextLine();
}
for (int a = 1; a > 0; a++) {
System.out.println("\nenter name to find number:\n");
String name2 = myScan.nextLine();
for (int b = 0; b < 200; b++) {
if (name2.equals(name[b])) {
System.out.println("number is " + number[b]);
break;
}
}
System.out.println("----THE NAME IS NOT IN THE LIST----\n");
}
}
}

Add a flag for when you find a name that matches user's input and dont print out last line when you find match, for that you could change your code like this:
for (int a = 1; a > 0; a++) {
System.out.println("\nenter name to find number:\n");
String name2 = myScan.nextLine();
boolean isNameFound = false;
for (int b = 0; b < 200; b++) {
if (name2.equals(name[b])) {
System.out.println("number is " + number[b]);
isNameFound = true;
break;
}
}
if (!isNameFound)
System.out.println("----THE NAME IS NOT IN THE LIST----\n");
}

Using a map will simplify this
Map<> contactBook = new Hashmap<>()
//then load the map using the phone number and name
You can also use data structure which will not allow dup names

Process of how do I spot the errors in this buggy code?

I have this code:
When I launch it, I am able to get numbers i = 0 to i = 10. However I know this is not the objective of the code as the objective is to reach into the Scanner. But the scanner does not seem to work? Am I making an error importing a file or is this to do with the code? I'm noob.
package buggyProgram;
import java.util.Scanner;
public class BuggyProgram {
/**
* The main method of the program. This is where it all starts.
*/
public static void main(String[] args) {
String[] saNames = new String[5];
String[] saNumbers = new String[5];
Scanner scIn = new Scanner(System.in);
for (int i = 0; i <= 4; i++) {
System.out.print("Enter name: ");
saNames[i] = scIn.nextLine();
System.out.print("Enter number: ");
saNumbers[i] = scIn.nextLine();
}
System.out.println();
for (int i = 1; i < 4; i++) {
System.out.println("The number of " + saNames[i] + " is "
+ saNames[i] + ".");
}
}
}

Java arrays start at 0 (not 1), and you're printing the same array element twice (in your second for-loop). Finally, you could always use a debugger to help you determine where things are no longer working as you expect.
// for (int i = 1; i < 4; i++) {
for (int i = 0; i <= 4; i++) { // <-- to match your first loop.
System.out.println("The number of " + saNames[i] + " is "
+ saNumbers[i] + ".");
}
You might also use formatted output (the formatter syntax) like
for (int i = 0; i <= 4; i++) {
System.out.printf("The number of %s is %s.%n", saNames[i], saNumbers[i]);
}

One of the first things you can do to make it easier to debug is to make the input fixed between runs. If you change Scanner scIn = new Scanner(System.in); to this:
Scanner scIn = new Scanner(new BufferedReader(new FileReader("some-file.txt")));
Assuming that some-file.txt is populated with the appropriate input, then you can run the program multiple times without having to manually re-enter the input. In addition, the input is fixed, so comparing the output of different runs becomes more useful.

I can confirm, that your code works, as long as you change your final output:
String[] saNames = new String[5];
String[] saNumbers = new String[5];
Scanner scIn = new Scanner(System.in);
for (int i = 0; i <= 4; i++) {
System.out.print("Enter name: ");
saNames[i] = scIn.nextLine();
System.out.print("Enter number: ");
saNumbers[i] = scIn.nextLine();
}
System.out.println();
for (int i = 1; i < 4; i++) {
System.out.println("The number of " + saNames[i] + " is "
+ saNumbers[i] + ".");
}