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Need help attaching a number from one array to its corresponding string in another array

For the code below, I am trying to input a n number of names name and marks. The code then reads the inputs and spits out the avg of marks and the highest and lowest marks names.
I have had some issues linking the max and min marks name to the marks themselves. I setup two arrays but am not sure how to track the position of the max and min mark to then link them to their corresponding name.
import java.util.Scanner;
public class Marks {
public static void main(String[] args) {
//It all goes in here
Scanner sc = new Scanner(System.in);
System.out.print("How many students are there? ");
int n = sc.nextInt();
String[] names = new String[n];
int[] marks = new int[n];
for (int i = 0; i < n; i++) {
System.out.print("Enter name of student " + (i + 1) +": " );
names[i] = sc.next();
System.out.print("Enter mark " + (i + 1) +": ");
marks[i] = sc.nextInt();
}
float sum = 0;
for (int i = 0;i < n;i++) {
sum += marks[i];
}
float average = (sum / marks.length);
System.out.println("The average mark is: " + average);
int maxMark = marks[0];
for (int i = 0;i < n; i++){
if (marks[i] > maxMark){
maxMark = marks[i];
}
}
int minMark = marks[0];
for (int i = 0;i < n; i++){
if (marks[i] < minMark){
minMark = marks[i];
}
}
System.out.println("The best student is " + maxMark);
System.out.println("The worst student is " + minMark);
}
}

There are several ways of doing that. For example, you can store index of the student along with max/min mark:
int minMark = marks[0];
int minMarkIndex = 0;
for (int i = 0;i < n; i++){
if (marks[i] < minMark){
minMark = marks[i];
minMarkIndex = i;
}
And then use this index to display student's name:
System.out.println("The student with minimal mark is ", names[minMarkIndex]);
More advanced approach is to create class Student. One of classes use cases is to encapsulate certain data. In this case, we'll encapsulate student's name and student's mark:
class Student {
public String name;
public int mark;
Student(String name, int mark) {
this.name = name;
this.mark = mark;
}
}
Note that there are a lot of conventions in terms of class definition, and class fields are seldom marked public, but it's okay for explanation.
And then, you store user input in instances of Student class. These instances are then used to retrieve data that is stored in them:
Student[] students = new Student[n];
for (int i = 0; i < n; i++) {
students[i] = new Student(names[i], marks[i]);
}
Student studentWithLowestMark = students[0], studentWithHighestMark = students[0];
for (Student student : students) { // iterates through students array, student == students[i]
if(student.mark < studentWithLowestMark.mark) {
studentWithLowestMark = student;
}
if(student.mark > studentWithHighestMark.mark) {
studentWithHighestMark = student;
}
}
System.out.println("Student with highest mark " + studentWithHighestMark.mark
+ " is " studentWithHighestMark.name);
System.out.println("Student with lowest mark " + studentWithLowestMark.mark
+ " is " studentWithLowestMark.name);
Opposite to first approach, this approach couples student's name and mark, so you can't by mistake use name of one student and mark of other:
// First approach allows this
System.out.println("Student " + names[0] + " has mark " + marks[1]) // Incorrect!
// Second approach simplifies the usage and preserves this type of error
System.out.println("Student " + student.name + " has mark " + student.mark);

My Java program refuses to take a string input [duplicate]

This question already has answers here:
Scanner is skipping nextLine() after using next() or nextFoo()?
(25 answers)
Closed 4 years ago.
I have an array of strings - name[]. When I try to take an input from the user using the Scanner class the program seems to ignore the statement and go on to the next.
import java.util.Scanner;
class Student { //start of class
public static void main(String[] args) { //start of method main
Scanner sc = new Scanner(System.in);
System.out.print("Enter number of students: ");
int n = sc.nextInt();
String name[] = new String[n];
int totalmarks[] = new int[n];
for (int i = 0; i < n; i++) {
System.out.println("Student " + (i + 1));
System.out.print("Enter name: ");
name[i] = sc.nextLine();
System.out.print("Enter marks: ");
totalmarks[i] = sc.nextInt();
}
int sum = 0;
for (int i = 0; i < n; i++) {
sum = sum + totalmarks[i]; //calculating total marks
}
double average = (double) sum / n;
System.out.println("Average is " + average);
for (int i = 0; i < n; i++) {
double deviation = totalmarks[i] - average;
System.out.println("Deviation of " + name[i] + " is " + deviation);
}
} //end of method main
} //end of class

That's because the sc.nextInt() method does not read the newline character in your input and so you need to call sc.nextLine()
From the docs
Advances this scanner past the current line and returns the input that
was skipped.
This method returns the rest of the current line, excluding any line
separator at the end. The position is set to the beginning of the next
line.
Since this method continues to search through the input looking for
a line separator, it may buffer all of the input searching for the
line to skip if no line separators are present.
You code will now look like :
public static void main(String[] args) {
Scanner sc = new Scanner(System.in);
System.out.print("Enter number of students: ");
int n = sc.nextInt();
sc.nextLine(); // <----- observe this
String name[] = new String[n];
int totalmarks[] = new int[n];
for (int i = 0; i < n; i++) {
System.out.println("Student " + (i + 1));
System.out.print("Enter name: ");
name[i] = sc.nextLine();
System.out.print("Enter marks: ");
totalmarks[i] = sc.nextInt();
sc.nextLine(); // <----- observe this
}
int sum = 0;
for (int i = 0; i < n; i++) {
sum = sum + totalmarks[i];
}
double average = (double) sum / n;
System.out.println("Average is " + average);
for (int i = 0; i < n; i++) {
double deviation = totalmarks[i] - average;
System.out.println("Deviation of " + name[i] + " is " + deviation);
}
}

Try this.. Your sc.nextLine() is reading empty String after you input integer value
import java.util.Scanner;
class Student
{//start of class
public static void main(String[] args)
{//start of method main
Scanner sc = new Scanner(System.in);
System.out.print("Enter number of students: ");
int n = sc.nextInt();
String emp = sc.nextLine();
String name[] = new String[n];
int totalmarks[] = new int[n];
for (int i=0;i<n;i++)
{
System.out.println("Student " + (i + 1));
System.out.print("Enter name: ");
name[i] = sc.nextLine();
System.out.print("Enter marks: ");
totalmarks[i] = sc.nextInt();
emp = sc.nextLine();
}
int sum = 0;
for (int i = 0; i < n; i++)
{
sum = sum + totalmarks[i];//calculating total marks
}
double average = (double) sum / n;
System.out.println("Average is " + average);
for (int i = 0; i < n; i++)
{
double deviation = totalmarks[i] - average;
System.out.println("Deviation of " + name[i] + " is " + deviation);
}
}//end of method main
}//end of class

How to calculate sum of elements of an array

I have this code where I'm able to calculate the average of marks but unable to calculate the sum and percentage.
And I want to print the name of the student under student name but I'm getting only the student number.
I tried understand more about these, but was unable to get through.
Could you please help me out?
package cube;
import java.io.*;
import java.util.Scanner;
public class ReportCard {
BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
int DB[][], nos = 0;
String arrayOfNames[] = new String[nos];
String S = "";
Scanner s = new Scanner(System.in);
void Input() throws Exception {
System.out.print("Enter The Number Of Students : ");
nos = Integer.parseInt(br.readLine());
DB = new int[nos + 1][6];
for (int i = 0; i < arrayOfNames.length; i++) {
System.out.print("Enter the name of student:");
arrayOfNames[i] = s.nextLine();
System.out.print("\nEnter " + arrayOfNames[i] + "'s English Score : ");
DB[i][0] = Integer.parseInt(br.readLine());
System.out.print("Enter " + arrayOfNames[i] + "'s Science Score : ");
DB[i][1] = Integer.parseInt(br.readLine());
System.out.print("Enter " + arrayOfNames[i] + "'s Maths Score : ");
DB[i][2] = Integer.parseInt(br.readLine());
DB[i][3] = (int) (DB[i][0] + DB[i][1] + DB[i][2] / 3); //calculating the Average Marks of Each Student
DB[i][4] = (int) (DB[i][0] + DB[i][1] + DB[i][2]);
}
}
void PrintReport() {
System.out.println("\nGenerated Report Card :\n\nStudent Name. English Science Maths Average Total\n");
for (int i = 0; i < nos; i++) {
Padd("Student Name. ", (i + 1));
Padd("English ", DB[i][0]);
Padd("Science ", DB[i][1]);
Padd("Maths ", DB[i][2]);
Padd("Average", DB[i][3]);
Padd("Total", DB[i][4]);
System.out.println(S);
S = "";
}
}
void Padd(String S, int n) {
int N = n, Pad = 0, size = S.length();
while (n != 0) {
n /= 10;
Pad++;
}
System.out.print(" " + N);
for (int i = 0; i < size - Pad - 5; i++)
System.out.print(" ");
}
public static void main(String args[]) throws Exception {
ReportCard obj = new ReportCard();
obj.Input();
obj.PrintReport();
}
}

You are initializing your arrayOfNames array to a length of zero always. You should be initializing it once you get the value of the variable nos ( similar to your initialization of 2d array DB)

You are creating the array of names, i.e, arrayOfNames as an array of length 0 because nos is initially zero.
Observe this:
int DB[][],nos=0; //nos is initialized to 0
String arrayOfNames[] = new String[nos]; //arrayOfNames is of size = nos,which is in turn equal to 0, hence arrayOfNames is basically an array which can't hold anything.
instead do this: just declare arrayOfNames and don't initialize it. ==> String arrayOfNames[];
define the string size after you accept the size, i.e, nos. So it should be as follows:
void Input() throws Exception {
System.out.print("Enter The Number Of Students : ");
nos = Integer.parseInt(br.readLine());
arrayOfNames[] = new String[nos]; //now define the size
...
This would ensure that the string is accessible outside the Input() function as well as is defined with a valid size.

Following corrections can make your code run..
package testProgram;
import java.io.BufferedReader;
import java.io.InputStreamReader;
import java.util.Scanner;
public class ReportCard {
BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
int DB[][], nos = 0;
//here initaialise reference will null
String arrayOfNames[] = null;
String S = "";
Scanner s = new Scanner(System.in);
void Input() throws Exception {
System.out.print("Enter The Number Of Students : ");
nos = Integer.parseInt(br.readLine());
DB = new int[nos + 1][6];
//create string array object here
arrayOfNames = new String[nos];
for (int i = 0; i < arrayOfNames.length; i++) {
System.out.print("Enter the name of student:");
arrayOfNames[i] = s.nextLine();
System.out.print("\nEnter " + arrayOfNames[i] + "'s English Score : ");
DB[i][0] = Integer.parseInt(br.readLine());
System.out.print("Enter " + arrayOfNames[i] + "'s Science Score : ");
DB[i][1] = Integer.parseInt(br.readLine());
System.out.print("Enter " + arrayOfNames[i] + "'s Maths Score : ");
DB[i][2] = Integer.parseInt(br.readLine());
//take extra variable that holds total, it increases the readability of the code
int total = DB[i][0] + DB[i][1] + DB[i][2];
DB[i][3] = (total) / 3; //calculating the Average Marks of Each Student
DB[i][4] = total;
}
}
void PrintReport() {
System.out.println("\nGenerated Report Card :\n\nStudent Name. English Science Maths Average Total\n");
for (int i = 0; i < nos; i++) {
Padd("Student Name. ", (i + 1));
Padd("English ", DB[i][0]);
Padd("Science ", DB[i][1]);
Padd("Maths ", DB[i][2]);
Padd("Average", DB[i][3]);
Padd("Total", DB[i][4]);
System.out.println(S);
S = "";
}
}
void Padd(String S, int n) {
int N = n, Pad = 0, size = S.length();
while (n != 0) {
n /= 10;
Pad++;
}
System.out.print(" " + N);
for (int i = 0; i < size - Pad - 5; i++)
System.out.print(" ");
}
public static void main(String args[]) throws Exception {
ReportCard obj = new ReportCard();
obj.Input();
obj.PrintReport();
}
}

Arrays are not dynamic. either you declare its size before hand or you use Arraylist..
boolean loopNaming = true;
int i = 0;
//you are creating array of zero size, use ArrayList instead
// String[] name = new String[i];
ArrayList<String> nameList = new ArrayList<>();
while (loopNaming == true) {
System.out.printf("Enter name of student or done to finish: ");
String name = keyboard.nextLine();
//check if name is 'done'
if (name.equals("done")) {
loopNaming = false;
} else {
nameList.add(name);
System.out.println("Enter score: ");
score = keyboard.nextDouble();
//nextLine positions cursor to next line
keyboard.nextLine();
}
i = i + 1;
}
System.out.println(nameList);

Name and age application with specific output using arrays and output

For my university lab work we have to finish 4 tasks. I'm currently on 6 of 9 and have for the most part completed it, but I'm having difficulty in completing the final parts of it. This is the description of what we must do:
Write a program that defines two arrays - one of strings and one of integers, both of size 10.
Your program should then ask the user to enter the a string representing a persons name,
and an integer representing their age. It should continue to do this until either the user
enters ‘done’ instead of a name, or until the array is full (that is, 10 pairs of names and ages
have been entered). It should then print out the names and ages as well as the names of the
youngest and oldest.
Hint: One tricky part is making sure that once you’ve typed ‘done’ to Finish entering names,
your program does not then ask you for the age of the person with name ‘done’ - be careful
about this.
I've highlighted the issues I'm having above in bolded text. Below is the code I currently have, but I'm not sure how to properly accomplish the bolded text.
import java.util.Scanner;
import java.util.Arrays;
import java.util.Collections;
public class nameAge {
public static void main(String[] args){
String[] name = new String[10];
int[] age = new int[10];
Scanner in = new Scanner(System.in);
String NAME_REQUEST = ("Please enter name");
String AGE_REQUEST = ("Please enter age");
System.out.println("Please enter the name of a person and then their age. Do this for up to 10 people and once finished, type 'done'");
name[0] = in.nextLine();
System.out.println(AGE_REQUEST);
age[0] = in.nextInt();
System.out.println(NAME_REQUEST);
name[1] = in.next();
System.out.println(AGE_REQUEST);
age[1] = in.nextInt();
System.out.println(NAME_REQUEST);
name[2] = in.next();
System.out.println(AGE_REQUEST);
age[2] = in.nextInt();
System.out.println(NAME_REQUEST);
name[3] = in.next();
System.out.println(AGE_REQUEST);
age[3] = in.nextInt();
System.out.println(NAME_REQUEST);
name[4] = in.next();
System.out.println(AGE_REQUEST);
age[4] = in.nextInt();
System.out.println(NAME_REQUEST);
name[5] = in.next();
System.out.println(AGE_REQUEST);
age[5] = in.nextInt();
System.out.println(NAME_REQUEST);
name[6] = in.next();
System.out.println(AGE_REQUEST);
age[6] = in.nextInt();
System.out.println(NAME_REQUEST);
name[7] = in.next();
System.out.println(AGE_REQUEST);
age[7] = in.nextInt();
System.out.println(NAME_REQUEST);
name[8] = in.next();
System.out.println(AGE_REQUEST);
age[8] = in.nextInt();
System.out.println(NAME_REQUEST);
name[9]= in.next();
System.out.println(AGE_REQUEST);
age[9] = in.nextInt();
System.out.println(NAME_REQUEST);
int size = name.length;
int sizeN = age.length;
for (int i=0; i < size; i++) {
System.out.println("Name: " + name[i]);
System.out.println("Age: " + age[i]);
}
int smallest = age[0];
int largetst = age[0];
for(int i=1; i< age.length; i++)
{
if(age[i] > largetst)
largetst = age[i];
else if (age[i] < smallest)
smallest = age[i];
}
System.out.println("Largest Number is : " + largetst);
System.out.println("Smallest Number is : " + smallest);
}
}

You have to take a look on loop doc in java
this code may help you
public static void main(String[] args) {
int youngest =0,older=0;
String[] name = new String[10];
int[] age = new int[10];
String NAME_REQUEST = ("Please enter name");
String AGE_REQUEST = ("Please enter age");
for(int i=0 ; i< 10;i++){
Scanner in = new Scanner(System.in);
System.out.println(NAME_REQUEST);
String tmpName = in.nextLine();
if(tmpName.equalsIgnoreCase("done"))
break;
name[i] = tmpName;
System.out.println(AGE_REQUEST);
age[i] = in.nextInt();
if(age[i] > age[older])
older = i;
if(age[i] < age[youngest])
youngest = i;
}
System.out.println("OLDER is : " + name[older]);
System.out.println("Younger : " + name[youngest]);
}

Try this out, I have tested it and it's working fine. Hope that helps. Happy coding.
package com.pearson.nextgen.aggregatedsessionservice;
import java.util.Scanner;
public class NameAgeTest {
public static void main(String[] args) {
String[] name = new String[10];
int[] age = new int[10];
Scanner in = new Scanner(System.in);
String NAME_REQUEST = "Please enter name";
String AGE_REQUEST = "Please enter age";
int count = 0;
while (count < 10) {
System.out.println(NAME_REQUEST);
String nameInput = in.next();
if (nameInput.equalsIgnoreCase("done")) {
break;
}
name[count] = nameInput;
System.out.println(AGE_REQUEST);
age[count] = in.nextInt();
count++;
}
int[] minAndMaxIndex = findMinAndMaxIndex(age, count);
System.out.println("Youngest Person: " + name[minAndMaxIndex[0]]);
System.out.println("Oldest Person: " + name[minAndMaxIndex[1]]);
}
private static int[] findMinAndMaxIndex(int[] inputArray, int count) {
int min, max = 0;
int minIndex = 0, maxIndex = 0;
max = min = inputArray[0];
for (int i = 0; i < count; i++) {
if (inputArray[i] > max)
maxIndex = i;
else if (inputArray[i] < min)
minIndex = i;
}
return new int[] { minIndex, maxIndex };
}
}

Ending a program with ctrl+Z

import java.util.Scanner;
public class ClassAverage
{
public static void main(String args[])
{
String names[] = new String[50];
int scores[] = new int[50];
int entries = 0;
Scanner in = new Scanner(System.in);
//System.out.println("Enter number of entries");
//int entry = in.nextInt();
System.out.println("Enter the names followed by scores of students: ");
for(int i = 0; i < 50; i++)
{
names[i] = in.next();
scores[i] = in.nextInt();
entries++;
}
Average avg = new Average();
double average = avg.CalcAvg(scores,entries);
System.out.println("The class average is: " + average);
avg.belowAvg(scores,average,names,entries);
avg.highestScore(scores,names, entries);
}
}
class Average
{
Average()
{
System.out.println("The averages: ");
}
double CalcAvg(int scores[], int entries)
{
double avg;
int total = 0;
for(int i = 0; i < entries; i++)
{
total += scores[i];
}
avg = total/entries;
return avg;
}
void belowAvg(int scores[],double average,String names[], int entries)
{
for(int i = 0; i < entries; i++)
{
if(scores[i] < average)
System.out.println(names[i] + "You're below class average");
}
}
void highestScore(int scores[],String names[], int entries)
{
int max = scores[1];
for(int i = 0; i < entries; i++)
{
if(scores[i]>=max)
max=scores[i];
}
System.out.println("The maximum score is: " + max);
System.out.println("The highest score acheivers list: ");
for(int i = 0; i < entries; i++)
{
if(scores[i] == max)
System.out.println(names[i]);
}
}
}
im suppose to hold the ctrlkey press z and then press the enter key to end the program but how do i do that?
if you are wondering the program is to write a program that lets the user input student names followed by their test scores and outputs the class average, names of students below the average, and the highest test score with the name of student

Ctrl-Z is the DOS command code for end of input (the UNIX equivalent is Ctrl-D). All command line programs should support this because it allows you to pipe output from one as input to the other. Kudos to your teacher!
When this key combo is pressed, Scanner.hasNextLine() will return false. Here's an example of a loop that reads line until you hit Ctrl-Z on Windows (or Ctrl-D on Linux/Unix):
while (in.hasNextLine()) {
System.out.println("You wrote " + in.nextLine());
}

You can listen for the control-z character in your scanner:
String nextLine = in.nextLine();
if(nextLine.length == 1 && nextLine.charAt(0) == KeyEvent.VK_Z)
// end program