如何用另一个字符串数组对double数组进行排序？

Question

I try to sort a double array but with another string array: It means I have this:

Double[] values = {6.3, 5.5 , 7.0};
String [] names ={"samah","Dalal", "Mohammad"};

samah has 5.5 , Dalal has 6.3 and Mohammad has 7.0

If I want to sort double values, it is simple using this:

Arrays.sort(values);

In this case the result is {5.5,6.3,7.0}

But how I will keep the names array with this sort?? result must be: {"Dalal","samah","Mohammad"}

Thanks

Answer 1

Add a new type that contains both values and implement Comparable .

public class Person implements Comparable<Person> {

  private String name;
  private double score;

  public Person(final String name, final double score) {
    this.name = name;
    this.score = score;
  }

  public String getName() {
      return name;
  }

  public void setName(final String name) {
      this.name = name;
  }

  public double getScore() {
      return score;
  }

  public void setScore(final double score) {
      this.score = score;
  }

  @Override
  public int compareTo(final Person another) {
      return Double.compare(score, another.score);
  }
}

Now an array of Person should order by score when sorted with Arrays.sort() .

Answer 2

Correct me if I am wrong, the objective is to store names and their corresponding values correctly, if that is the case then,

Why are you using two different arrays ? Why don't you read values and names in a map?

If you read them in a map you won't have to face issues of maintaining the order of names and values. If you do this the need for sorting will be reduced.

Answer 3

Use TreeMap with keys as the double data and values as the String data. TreeMap is sorted automatically by its keys.

Answer 4

You can also solve this using Comparator . If you want sort based on marks, use PersonMarksComparator , If you want to sort it based on name use PersonNameComparator . It will be very useful if you want to sort it on multiple ways.

class PersonMarksComparator implements Comparator<Person> {

  @Override
  public int compare(Person person1, Person person2) {
      return Double.compare(person1.getMarks(), person2.getMarks());
  }
}

class PersonNameComparator implements Comparator<Person> {

  @Override
  public int compare(Person person1, Person person2) {
      return person1.getName().compareTo(person2.getName());
  }
}

public class Person {

   private String name;
   private double marks;

   public Person(final String name, final double marks) {
      this.name = name;
      this.marks = marks;
   }

   //getters and setters

   public static void main(String[] args) {
      List<Person> persons = new ArrayList<Person>();
      Person person1 = new Person("samah", 5.5);
      Person person2 = new Person("Dalal", 6.3);
      Person person3 = new Person("Mohammad", 7.0);
      persons.add(person1);
      persons.add(person2);
      persons.add(person3);
      Collections.sort(persons, new PersonMarksComparator());
      Collections.sort(persons, new PersonNameComparator());
  }
}

Answer 5

Try this. (for Java8)

Double[] values = {6.3, 5.5 , 7.0};
String [] names ={"samah","Dalal", "Mohammad"};
String[] sortedNames = IntStream.range(0, names.length)
    .mapToObj(i -> i)
    .sorted(Comparator.comparing(i -> values[i]))
    .map(i -> names[i])
    .toArray(String[]::new);
System.out.println(Arrays.toString(sortedNames));

result:

[Dalal, samah, Mohammad]

Process:

1. Make IntStream of indexes -> [0, 1, 2]
2. Convert each index to Integer object -> [0, 1, 2]
   (because IntStrem has no sorted(Comparator) method)
3. Sort each index by values[index] -> [1, 0, 2]
4. Map each index to names[index] -> ["Dalal", "samah", "Mohamand"]
5. Save the result as an array -> ["Dalal", "samah", "Mohamand"]