Java 컬렉션 정렬

Java 컬렉션 정렬

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Java 컬렉션이 있습니다.

Collection<CustomObject> list = new ArrayList<CustomObject>();

CustomObject이 id필드는 현재 표시 목록 전에 그하여이 컬렉션을 정렬 할 id.

그렇게 할 수있는 방법이 있습니까?

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비교기 사용 :

List<CustomObject> list = new ArrayList<CustomObject>();
Comparator<CustomObject> comparator = new Comparator<CustomObject>() {
    @Override
    public int compare(CustomObject left, CustomObject right) {
        return left.getId() - right.getId(); // use your logic
    }
};

Collections.sort(list, comparator); // use the comparator as much as u want
System.out.println(list);

또한을 CustomObject구현 Comparable하는 경우Collections.sort(list)

JDK 8에서는 구문이 훨씬 간단합니다.

List<CustomObject> list = getCustomObjectList();
Collections.sort(list, (left, right) -> left.getId() - right.getId());
System.out.println(list);

훨씬 간단

List<CustomObject> list = getCustomObjectList();
list.sort((left, right) -> left.getId() - right.getId());
System.out.println(list);

가장 간단

List<CustomObject> list = getCustomObjectList();
list.sort(Comparator.comparing(CustomObject::getId));
System.out.println(list);

분명히 초기 코드는 JDK 8에도 사용할 수 있습니다.

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질문은 "Sort Collection"입니다. 따라서 Collections.sort(List<T> l, Comparator<? super T> comparator).

몇 가지 팁 :

컬렉션 유형 :

Comparator<String> defaultComparator = new Comparator<String>() {
   @Override
   public int compare(String o1, String o2) {
       return o1.compareTo(o2);
   }
};

Collection<String> collection = getSomeStringCollection();
String[] strings = collection.toArray(new String[collection.size()]);
Arrays.sort(strings, defaultComparator);
List<String> sortedStrings = Arrays.asList(strings);

Collection<String> collection = getSomeStringCollection();
List<String> list = new ArrayList(collection);
Collections.sort(list, defaultComparator);
collection = list; // if you wish

목록 유형 :

List<String> list = getSomeStringList();
Collections.sort(list, defaultComparator);

세트 유형 :

Set<String> set = getSomeStringSet();
// Than steps like in 'For Collection type' section or use java.util.TreeSet
// TreeSet sample:
// Sorted using java.lang.Comparable.
Set<String> naturalSorted = new TreeSet(set);

Set<String> set = getSomeStringSet();
Set<String> sortedSet = new TreeSet(defaultComparator);
sortedSet.addAll(set);

Java 8 버전. 이 java.util.List#sort(Comparator<? super E> c)방법은

List<String> list = getSomeStringList();
list.sort(defaultComparator);

또는

List<String> list = getSomeStringList();
list.sort((String o1, String o2) -> o1.compareTo(o2));

또는 Comparable을 구현하는 유형의 경우 :

List<String> list = getSomeStringList();
list.sort(String::compareTo);

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Comparable을 구현하지 않는 클래스가 있지만 여전히 필드 또는 메서드에서 정렬하려는 경우 약간 다른 예가 있습니다.

Collections.sort(allMatching, new Comparator<ClassOne>() {
  @Override public int compare(final ClassOne o1, final ClassOne o2) {
    if (o1.getMethodToSort() > o2.getMethodToSort()) {
      return 1;
    } else if (o1.getMethodToSort() < o2.getMethodToSort()) {
      return -1;
    }  
    return 0;
  }
});

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You should implement the Comparator interface.

example:

public class CustomComparator implements Comparator<CustomObject> 
{
    @Override
    public int compare(CustomObject o1, CustomObject o2) {
        return o1.getId().compareTo(o2.getId());
    }
}

Then you can use the Collections classes Collections.sort() method:

Collections.sort(list, new CustomComparator());

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Implement the Comparable interface on your customObject.

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Comparator is the way

Also See

• sorting-of-arraylist

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As of Java 8 you now can do it with a stream using a lambda:

list.stream().sorted(Comparator.comparing(customObject::getId))
             .foreach(object -> System.out.println(object));

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A lot of correct answers, but I haven't found this one: Collections cannot be sorted, you can only iterate through them.

Now you can iterate over them and create a new sorted something. Follow the answers here for that.

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Use sort.

You just have to do this:

All elements in the list must implement the Comparable interface.

(Or use the version below it, as others already said.)

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SortedSet and Comparator. Comparator should honour the id field.

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With Java 8 you have several options, combining method references and the built-in comparing comparator:

import static java.util.Comparator.comparing;

Collection<CustomObject> list = new ArrayList<CustomObject>();

Collections.sort(list, comparing(CustomObject::getId));
//or
list.sort(comparing(CustomObject::getId));

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You can use java Custom Class for the purpose of sorting.

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You can also use:

Collections.sort(list, new Comparator<CustomObject>() {
    public int compare(CustomObject obj1, CustomObject obj2) {
        return obj1.id - obj2.id;
    }
});
System.out.println(list);

참고URL : https://stackoverflow.com/questions/6957631/sort-java-collection