Student's names(String[]) and corresponding marks(int[]) are stored in different arrays.
How may I iterate over both arrays together using for each loop in Java ?
void list() {
for(String s:studentNames) {
System.out.println(s); //I want to print from marks[] alongside.
}
}
One trivial way could be using index variable in the same loop. Is there a good way to do?
You need to do it using the regular for loop with an index, like this:
if (marks.length != studentNames.length) {
... // Something is wrong!
}
// This assumes that studentNames and marks have identical lengths
for (int i = 0 ; i != marks.length ; i++) {
System.out.println(studentNames[i]);
System.out.println(marks[i]);
}
A better approach would be using a class to store a student along with his/her marks, like this:
class StudentMark {
private String name;
private int mark;
public StudentMark(String n, int m) {name=n; mark=m; }
public String getName() {return name;}
public int getMark() {return mark;}
}
for (StudentMark sm : arrayOfStudentsAndTheirMarks) {
System.out.println(sm.getName());
System.out.println(sm.getMark());
}
The underlying problem is actually that you should tie both of the arrays together and iterate across just one array.
Here is a VERY simplistic demonstration - you should use getters and setters and you should also use a List instead of an array but this demonstrates the point:
class Student {
String name;
int mark;
}
Student[] students = new Student[10];
for (Student s : students) {
...
}
If them both have the same size, I would write:
for(int i = 0; i<marks.length; i++) {
String names= studentNames[i]
int mark = marks[i];
}
The other way is to use a verbose for loop statement such as;
int i,j;
for(i = 0, j=0; i<= student.length-1 && j <=grades.length-1; i++,j++)
{
...
}
Related
In below code string is passed in a method with numbers separated by space,
now we need to provide sum of smallest two numbers in the string.
public class SumNearZero {
public static int SumNearZero(String s) {
String temp=s;
int t1=0;
for (int i = 0; i <s.length(); i++) {
if(temp.contains(" "))
{
t1++;
temp=temp.substring(temp.indexOf(" ")+1);
}
}
int a[]=new int[++t1];
int index=0;
for(int i=0; i<s.length(); i++)
{
if(s.contains(" "))
{
a[index]=Integer.parseInt(s.substring(0,s.indexOf(" ")));
s=s.substring(s.indexOf(" ")+1);
index++;
}
}
a[index]=Integer.parseInt(s);
for (int i = 0; i < a.length; i++) {
for(int j=0; j<a.length-1; j++)
{
int c=a[j],n=a[j+1];
if(c>n)
{
int t=c;
a[j]=n;
a[j+1]=t;
} } }
int result=a.length>1 ? a[0]+a[1]:a[0];
return result;
}
public static void main(String[] args) {
System.out.println(SumNearZero("35 96 10 20 5"));
}
}
Above code is working fine but i want to reduce the code. if you provide some suggestion regarding this, I'll be happy to learn from you.
Restrictions : use of Collections, predefined methods e.g(String.split(),Arrays.sort()...)
I would suggest you not perform your calculation and display in a constructor, create a static method and invoke it. Next, in that method, create a List of Integer by iterating the substrings generated by splitting your input on one (or more) white space characters. Then, sort the List. Finally, return the sum of the first two elements1. It's also a good to do some error checking for one number (or no numbers). That might look something like
public static int sumNearZero(String s) {
List<Integer> al = new ArrayList<>();
for (String str : s.split("\\s+")) {
al.add(Integer.parseInt(str));
}
if (al.isEmpty()) {
return 0;
}
Collections.sort(al);
if (al.size() == 1) {
return al.get(0);
}
return (al.get(0) + al.get(1));
}
Then invoke it like
public static void main(String[] args) {
System.out.println(sumNearZero("35 96 10 20 5"));
}
I get (as I expected)
15
1once sorted the first two are the minimum, and the last two are the maximum
You can make it faster by using for each loop instead of for loop every time, it is more recommended and faster approach whenever loop is increasing for array, lists etc.
Plus more you can get all numbers in string by using split function which retrives you array of those numbers.and then you can put your logic for getting small numbers.this will reduce counting and increase speed highly in general if you want to learn about optimization then this is definitive guide i suggest you to go through it. and see this answer.
Looks like an exercise, so not giving actual code.
Use String.split and Arrays.sort
I am facing a problem where I need to sort a String array in alphabetical order. I am able to sort one array, but the problem starts when there are 2 more arrays, that correspond to the first array. Each value in each array should be in the same place, to make information not messed up. After sorting array1, it is in alphabetical order, but i don't have any idea how to make values from array2 and array3 change the positions the same like in array1 after sorting is finished.
My code so far is:
public void sort()
{
boolean finish = false;
while(finish == false){
finish = true;
for(int i=0;i<Country.length-1;i++)
{
int num = 0;
if(Country[i] != null && Country[i + 1] != null)
{
String name1=Country[i]; String name2=Country[i+1];
num=name1.compareTo(name2);
}
else if(Country[i] == null && Country[i + 1] == null){
num = 0;
}
else if(Country[i] == null){
num = 1;
}
else {
num = -1;
}
if(num>0)
{
String temp=Country[i];
Country[i]=Country[i+1];
Country[i+1]=temp;
finish=false;
}
}
}
By far the most recommended way is to re-design your program, and arrange all the related items in a single class. This is what objects are for, after all. Then you can make the object Comparable, give it a compareTo method, and sort it.
But if you are really unable to do that, what you should do is, whenever you exchange any two items in your sort array, make sure you exchange the corresponding items in the other arrays.
So, if you have arrays country, capital and headOfState, you will have to write something like:
String temp=country[i];
country[i]=country[i+1];
country[i+1]=temp;
temp=capital[i];
capital[i]=capital[i+1];
capital[i+1]=temp;
temp=headOfState[i];
headOfState[i]=headOfState[i+1];
headOfState[i+1]=temp;
This way, whenever you move anything in your main array, you'll also be moving the respective item in the other arrays, so they will stay together.
But again, it's much more preferred if you re-designed your program.
Also note the Java language conventions - variable names should not start with a capital letter, only type names should.
If you want all the array to be swaped based on the compare you did in the country array. You can just swap more than one array after one compare.
If(array1[i] > array1[i+1]){
Swap(array1[i],array1[i+1)
Swap(array2[i],array2[i+1])
}
By using a swap function, you can make it more simpler to do swaping in much more array.
You have to swap elements in Country and City arrays simultaneously.
public class BubbleSortTmp {
public String[] Country = {"z", "h", "a"};
public int[] City = {3, 2, 1};
public void printCountry() {
for (String s : Country) {
System.out.printf("%s ", s);
}
System.out.println();
}
public void printCity() {
for (int s : City) {
System.out.printf("%s ", s);
}
System.out.println();
}
public void sort() {
for (int outer = Country.length - 1; outer > 0; outer--) {
for (int inner = 0; inner < outer; inner++) {
if (Country[inner].compareTo(Country[inner+1]) > 0) {
swapCountry(inner, inner+1);
swapCity(inner, inner+1);
}
}
}
}
private void swapCountry(int first, int second) {
String tmp = Country[first];
Country[first] = Country[second];
Country[second] = tmp;
}
private void swapCity(int first, int second) {
int tmp = City[first];
City[first] = City[second];
City[second] = tmp;
}
public static void main(String[] args) {
BubbleSortTmp bs = new BubbleSortTmp();
System.out.println("Before: ");
bs.printCountry();
bs.printCity();
bs.sort();
System.out.println("After: ");
bs.printCountry();
bs.printCity();
}
}
The task was to create a program which organises a users name with their corresponding mark and displays this in descending order. I'm asking how to sort both arrays at the same time but only by comparing the elements of one of the arrays. As a restriction, I cannot use classes, only associated arrays.
int [] ArrMarks = new int [5];
String [] ArrNames = new String [5];
Button to Accept user input
for (int i = 0; i < 5; i++)
{
ArrNames[i] = JOptionPane.showInputDialog("Enter a Name:");
ArrMarks[i] = Integer.parseInt(JOptionPane.showInputDialog("Enter a mark:"));
}
Display button including the part which sorts the code, this is the main part I am unsure of.
int Hi = ArrMarks[0];
for(int i = 0; i < 5; i++) {
if(ArrMarks[i] > Hi) {
Hi = ArrMarks[i];
}
}
txaDisplay.append("Names:"+"\t\t"+"Marks");
for (int i = 0; i < 5; i++) {
txaDisplay.append(ArrNames[i]+"\t\t"+ArrMarks[i]+"\n");
}
First of all, I would like to give a suggestion. Use lists instead of arrays. This kind of coding is not a good conventional way of coding. I will show a conventional way to handle the issue. You may take this if you like.
Create another class Mark.java with the following content
class Mark {
Integer mark;
String name;
public Integer getMark() {
return this.mark
}
public void setMark(Integer mark) {
this.mark = mark
}
public String getName() {
return this.name
}
public void setName(String name) {
this.name = name
}
}
Then in your current class create a List of this class.
List<Mark> marks = new ArrayList<Mark>();
Then after reading content from the user, you can add them to the list like following
for (int i = 0; i < 5; i++)
{
Mark mark = new Mark();
String name = JOptionPane.showInputDialog("Name:");
Integer mark = Integer.parseInt(JOptionPane.showInputDialog("Mark:"));
marks.add(mark)
}
Write a comparator class named MarkComparator.java. It deals with the sorting part.
public class MarkComparator implements Comparator<Mark> {
#Override
public int compare(Mark m1, Mark m2) {
return m1.getMark().compareTo(m2.getMark());
}
}
The use
Collections.sort(marks, new MarkComparator());
Now the List<Mark> of marks will be sorted.
You may then view the list the same way.
txaDisplay.append("Names:"+"\t\t"+"Marks");
for (Mark mark : marks)
{
txaDisplay.append(mark.getName()+"\t\t"+mark.getMark()+"\n");
}
The solution to my question required using a sorting technique to sort the names and marks, so that the program prints the corresponding mark to the name.
for(int i = 0; i < 5-1; i ++)
{
for(int j = i +1; j < 5; j++)
{
if (ArrMarks[i] < ArrMarks[j])
{
//sorting the names
String temp = ArrNames[i];
ArrNames[i] = ArrNames[j];
ArrNames[j] = temp;
//sorting the marks
int temp1 = ArrMarks[i];
ArrMarks[i] = ArrMarks[j];
ArrMarks[j] = temp1;
}
}
txaDisplay.append("Names:"+"\t\t"+"Marks"+"\n");
txaDisplay.append(ArrNames[i]+"\t\t"+ArrMarks[i]+"\n");
}
I have been stuck on this problem for so long and i have no idea what to do.
Basically i have a text file with people names then student number then prize money like this:
Green%3243%1000
Kevin%7657%400
Frank%345%10000
Bob%5435%5000
Stefan%31231%1000
Javis%4532%100
IronMan%5435%2000
Lamp%534%3000
What i want to be able to do is sort the array based on the last number.
I tried this abomination (Don't bother reading it its garbage):
boolean flag = true;
String temp;
int temp1;
int temp2;
while (flag){
flag = false;
for(int j=0; j < list.size() -1; j++ ){
System.out.println(list.get(j));
Scanner s = new Scanner(list.get(j)).useDelimiter("%");
s.next();
s.next();
temp1 = s.nextInt();
Scanner s2 = new Scanner(list.get(j+1)).useDelimiter("%");
s2.next();
s2.next();
temp2 = s2.nextInt();
if (temp1 < temp2){
temp = list.get(j);
list.add(j, list.get(j+1));
list.add(j+1,temp);
flag = true;
}
}
}
But its just infinitely looping. My though while making it was just patching array lists into a bubble sort.
If anyone has any ideas and is willing to share them it will be greatly appreciated.
Java is an object-oriented language, so I'll just use objects:
Create a Student object with the three values you want to store (and a toString() method to print them separated by "%":
public class Student {
private final String name;
private final int number;
private final int prizeMoney;
public Student(final String name, final int number, final int prizeMoney) {
this.name = name;
this.number = number;
this.prizeMoney = prizeMoney;
}
#Override
public String toString() {
return name+"%"+number+"%"+prizeMoney;
}
public int getPrizeMoney() {
return prizeMoney;
}
}
Read your lines as Student objects, and store them in a List:
final Scanner scan = new Scanner(new File("/path/to/StudentsList"));
final List<Student> students = new ArrayList<Student>();
while (scan.hasNextLine()) {
final Scanner line = new Scanner(scan.nextLine());
line.useDelimiter("%");
students.add(new Student(line.next(), line.nextInt(), line.nextInt()));
line.close();
}
scan.close();
Order the List with a custom Comparator, and print it:
students.sort(new Comparator<Student>() {
#Override
public int compare(final Student s1, final Student s2) {
return s1.getPrizeMoney()-s2.getPrizeMoney();
}
});
for (final Student student: students)
System.out.println(student);
Output:
Javis%4532%100
Kevin%7657%400
Green%3243%1000
Stefan%31231%1000
IronMan%5435%2000
Lamp%534%3000
Bob%5435%5000
Frank%345%10000
Here's something for you to get head started.
Create a map for prize money => line as key/value pair
Read each line in the file, parse it and put key/value pair in the above map
Once your map is ready, convert the keys entry set into the collections like list
Sort the collections, using Collections.sort()
Iterate over the created map, and for each value in the collection get the corresponding value from the map.
Hope this helps you to get the workflow.
Id consider creating a 3d array here 8x8x8 from right to left in the array is row, col, and in so [0][0][1] is block one or kevin [0][1][1] is 7657 [1][1][1] is 400. I like this way because not only does it give each 'item' an array it allows you to keep it organized and easily accessable
I have three arrays in my proggramme Surname, Forename and result and need to create a sort array
Surname: Chris Forename: Charleton: Result: 54
Surname: Annett: forename: Lyle: result 67
If I wanted to sort it by alphabetical of last name, i need all the fields to move, instead of just the surname. This is the bubble sort code i'm working off
int swap;
boolean swapflag = true;
//outer loop
while (swapflag == true)
{
swapflag = false;
//inner loop
for (int index=0; index < (nums.length - 1); index++)
{
//swap routine
if (nums[index]> nums[index + 1])
{ //swap routine
swap = nums[index];
nums[index] = nums[index + 1];
nums[index + 1] = swap;
swapflag = true;
}
}//end inner
}//end outer
System.out.println ("\nArray Contents after sorting"
+ "\n*************");
for (int index=0; index < nums.length; index ++)
{
System.out.println("Array element "
+ index + ": " + nums[index]);
}
}
}
` package projStudent;
import java.util.Scanner;
public class UnitResults
{
//delcare Scanner as keyb
static Scanner keyb = new Scanner (System.in);
//declare fields
static String studentForename [];
static String studentSurname [];
static int [] studentResult;
static int pointer;
//constructor
UnitResults(int sizeofclass)
{//start of constructor
studentForename = new String [sizeofclass];
studentSurname = new String [sizeofclass];
studentResult = new int [sizeofclass];
pointer = 0;
}//end of constructor
public boolean add(String studentForename[], String studentSurname[],
int studentResult[])
{//start of add method
if (pointer == studentResult.length )
{//start of if statement
System.out.println("Sorry Array is full");
return false;
studentResult[pointer] = studentResult[];
pointer ++;
}//end of if statement
}//end of add method
public boolean delete(int element)
{//start of delete method
element = element - 1;
if ((element >= 0) && ( element < pointer))
{//start of if statement
for(int index = (element + 1); index < pointer; index++)
{//start of for statement
studentResult[index - 1] = studentResult[index];
}//end of for statement
pointer--;
return true;
}//end of if statement
else
{//start of else statement
return false;
}//end of else statement
}//end of delete method
public String find()
{//start of display
String strOutput="";
strOutput = strOutput + "Students";
if (pointer==0)
{//start of if statement
strOutput = strOutput + "There are no records in this Array";
return strOutput;
}//end of if statement
for (int index=0; index < pointer; index++)
{//start of for method
strOutput = strOutput + "Student Name" + studentSurname[index] + studentForename +
"Student Result" + studentResult +"\n";
}//end of for method
return strOutput;
}//display
public int sort (int UnitResults)
{//start of sort
int sort;
boolean swapflag = true;
while (swapflag == true)
{//start of while loop
swapflag = false;
for (int index=0; index < (UnitResults - 1); index++)
{
if (studentResult[index]> studentResult[index + 1])
{ //swap routine
sort = studentResult[index];
studentResult[index] = studentResult[index + 1];
studentResult[index + 1] = sort;
swapflag = true;
}
}
}//end of while loop
}//end of sort
}`
Unfortunately, your post is confusing as you don't include some things, like just what is the current array you are sorting. Still, if I understand your question correctly...
Regardless of the language, your strategy would involve changes to how you swap the elements. If your array consists of composite data, then simply assigning in a swap is fine. If your data is scattered, then your swap needs to swap each variable. You can always just sort the indices of the array into another array, then use that array to indirectly reference the first, for sorted access.
I would suggest you use an List for this purpose.
First create an object. For example "Person" containing members for "Forname","Surename","Result". Then fill the list with these objects, implement the Interface Compareable and use the Collection.sort() methode.
class Person implements Comparable<Person>
{
private String forname;
private String surname;
private int rating;
public Person(String forename, String surname, int rating)
{
this.forname = forename;
this.surname = surname;
this.rating = rating
}
public int compareTo(Person p) {
if(p.rating == this.rating)
return 0;
else if(p.rating < this.rating)
return -1;
return 1;
}
}
class Test{
public static void main(String[] args){
List<Person> personList = new ArrayList<Person>();
Person p1 = new Person("John","Smith",10);
Person p2 = new Person("Max","Muster",20);
Person p3 = new Person("Sarah","Clark",15);
personList.add(p1);
personList.add(p2);
personList.add(p3);
personList.sort();
}
}
There are a number of features of the Java programming languages that can help you resolve the problem that you are having, the first of which is inclusion of appropriate data structures and methods with which to manipulate objects within those data structures.
First and foremost, I'd recommend using a java class to represent a single person entity... think about it, when you look up a person's information, you don't consult three separate books, or computer screens, or what have you, when all that information can be organized into one place. For your person above, for example, you could use something like this:
public class Person implements Comparable<Person> {
public String firstName;
public String lastName;
public int result;
public Person(String fn, String ln, int r) {
firstName = fn;
lastName = ln;
result = r;
}
public int compareTo(Person otherPerson) {
return lastName.compareTo(otherPerson.lastName);
}
}
This will give you an object that will store all of your person information, and by default will be easily sortable by last name (you can change this behavior with a comparator, which I won't cover here.)
Now instead of having three different arrays of first names, last names, and results, you can have a single array of Persons. There ARE actually sorting mechanisms within the java language for arrays already, which you can research and use if you choose, but if you'd like to use your own sort, you would just need to replace your swap conditional with something like this:
if(persons[index].compareTo(persons[index+1]) > 0) {
...
}
i just want ask you
why instead creating class student ie
class Student{
private String studentForename;
private String studentSurname;
private int studentResult;
//setters and getters
}
and put them in some collection ie List
you are putting them into 3 different arrays?
do you realize, if you have them nicely in the list, you can sort them just by using Collections.sort() ?
Can't understand properly the question: are you looking for a way to manually implement a sorting algorithm (bubble, quick or whatever) or you would like to simply sort them the best you can? Generally speaking you should never implement your own sort 'cause Java provides itself a very efficient lot... or is this an exercise? Probably :)
Best way I can imagine is, provided the 3 arrays in their original form are linked by index, create a surname/index map, load it form surname array, sort the Map.Entry by key and then you will have the array indexes sorted the way you wanted. Check here for more details: how to sort Map values by key in Java
PS The solutions provided by the others are correct and preferrable if you are NOT doing an exercise :) Better deal with a structured object than with 3 separated data.