2.8.7. Sorted sets

<div class="paragraph">

For sorted sets, the entity mapping must use the `SortedSet` interface instead.
According to the `SortedSet` contract, all elements must implement the comparable interface and therefore provide the sorting logic.

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<div class="sect4">

##### Unidirectional sorted sets

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A `SortedSet` that relies on the natural sorting order given by the child element `Comparable` implementation logic must be annotated with the `@SortNatural` Hibernate annotation.

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<div id="collections-unidirectional-sorted-set-natural-comparator-example" class="exampleblock">
<div class="title">Example 160. Unidirectional natural sorted set</div>
<div class="content">
<div class="listingblock">
<div class="content">
<pre class="prettyprint highlight">`@Entity(name = "Person")
public static class Person {

    @Id
    private Long id;
    @OneToMany(cascade = CascadeType.ALL)
    @SortNatural
    private SortedSet&lt;Phone&gt; phones = new TreeSet&lt;&gt;();

    public Person() {
    }

    public Person(Long id) {
        this.id = id;
    }

    public Set&lt;Phone&gt; getPhones() {
        return phones;
    }
}

@Entity(name = "Phone")
public static class Phone implements Comparable&lt;Phone&gt; {

    @Id
    private Long id;

    private String type;

    @NaturalId
    @Column(name = "`number`")
    private String number;

    public Phone() {
    }

    public Phone(Long id, String type, String number) {
        this.id = id;
        this.type = type;
        this.number = number;
    }

    public Long getId() {
        return id;
    }

    public String getType() {
        return type;
    }

    public String getNumber() {
        return number;
    }

    @Override
    public int compareTo(Phone o) {
        return number.compareTo( o.getNumber() );
    }

    @Override
    public boolean equals(Object o) {
        if ( this == o ) {
            return true;
        }
        if ( o == null || getClass() != o.getClass() ) {
            return false;
        }
        Phone phone = (Phone) o;
        return Objects.equals( number, phone.number );
    }

    @Override
    public int hashCode() {
        return Objects.hash( number );
    }
}`</pre>
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<div class="paragraph">

The lifecycle and the database mapping are identical to the [Unidirectional bags](#collections-unidirectional-bag), so they are intentionally omitted.

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<div class="paragraph">

To provide a custom sorting logic, Hibernate also provides a `@SortComparator` annotation:

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<div id="collections-unidirectional-sorted-set-custom-comparator-example" class="exampleblock">
<div class="title">Example 161. Unidirectional custom comparator sorted set</div>
<div class="content">
<div class="listingblock">
<div class="content">
<pre class="prettyprint highlight">`@Entity(name = "Person")
public static class Person {

    @Id
    private Long id;

    @OneToMany(cascade = CascadeType.ALL)
    @SortComparator(ReverseComparator.class)
    private SortedSet&lt;Phone&gt; phones = new TreeSet&lt;&gt;();

    public Person() {
    }

    public Person(Long id) {
        this.id = id;
    }

    public Set&lt;Phone&gt; getPhones() {
        return phones;
    }
}

public static class ReverseComparator implements Comparator&lt;Phone&gt; {
    @Override
    public int compare(Phone o1, Phone o2) {
        return o2.compareTo( o1 );
    }
}

@Entity(name = "Phone")
public static class Phone implements Comparable&lt;Phone&gt; {

    @Id
    private Long id;

    private String type;

    @NaturalId
    @Column(name = "`number`")
    private String number;

    public Phone() {
    }

    public Phone(Long id, String type, String number) {
        this.id = id;
        this.type = type;
        this.number = number;
    }

    public Long getId() {
        return id;
    }

    public String getType() {
        return type;
    }

    public String getNumber() {
        return number;
    }

    @Override
    public int compareTo(Phone o) {
        return number.compareTo( o.getNumber() );
    }

    @Override
    public boolean equals(Object o) {
        if ( this == o ) {
            return true;
        }
        if ( o == null || getClass() != o.getClass() ) {
            return false;
        }
        Phone phone = (Phone) o;
        return Objects.equals( number, phone.number );
    }

    @Override
    public int hashCode() {
        return Objects.hash( number );
    }
}`</pre>
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<div class="sect4">

##### Bidirectional sorted sets

<div class="paragraph">

The `@SortNatural` and `@SortComparator` work the same for bidirectional sorted sets too:

</div>
<div id="collections-bidirectional-sorted-set-example" class="exampleblock">
<div class="title">Example 162. Bidirectional natural sorted set</div>
<div class="content">
<div class="listingblock">
<div class="content">
<pre class="prettyprint highlight">`@OneToMany(mappedBy = "person", cascade = CascadeType.ALL)
@SortNatural
private SortedSet&lt;Phone&gt; phones = new TreeSet&lt;&gt;();

@OneToMany(cascade = CascadeType.ALL)
@SortComparator(ReverseComparator.class)`</pre>
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<div class="sect3">