如何检查一组对象是否包含 object，该 object 的特定字段在 Java 中有特定值？

Question

I am working on a Spring Boot application and I am not so confidend with the new Java 8 features. I have the following problem.

In my code I have this service method:

@Override
public List<User> getClientsOfASubAgentUser(int subAgentId) throws NotFoundException {
    
    Optional<User> retrievedUser = this.userRepository.findById(subAgentId);
    
    if(retrievedUser.isEmpty()) {
        throw new NotFoundException(String.format("The SUB-AGENT user having ID or email %s was not found", Integer.toString(subAgentId)));
    }
    
    // CHECK IF THE Set<UserType> returned by the getUserTypes() method contain an object having "typeName" field value equals to "SUB-AGENT" 
    if(retrievedUser.get().getUserTypes().????)

    
    
    List<User> clientsList = this.userRepository.findByParent_Id(subAgentId);
    
    return clientsList;
}

My problem is on this line (that is incomplete):

// CHECK IF THE Set<UserType> returned by the getUserTypes() method contain an object having "typeName" field value equals to "SUB-AGENT" 
if(retrievedUser.get().getUserTypes().????)

The getUserTypes() return a Set . This is the UserType entity class:

@Entity
@Table(name = "user_type")
@Getter
@Setter
public class UserType implements Serializable {
    
    private static final long serialVersionUID = 6904959949570501298L;

    @Id
    @Column(name = "id")
    @GeneratedValue(strategy=GenerationType.IDENTITY)
    private int id;
    
    @Column(name = "type_name")
    private String typeName;
    
    @Column(name = "description")
    private String description;
    
    
    @ManyToMany(cascade = { CascadeType.MERGE })
    @JoinTable(
        name = "user_type_operation", 
        joinColumns = { @JoinColumn(name = "fk_user_type_id") }, 
        inverseJoinColumns = { @JoinColumn(name = "fk_operation_id") }
    )
    Set<Operation> operations;
    

    public UserType() {
        super();
        // TODO Auto-generated constructor stub
    }
    
    public UserType(String typeName, String description) {
        super();
        this.typeName = typeName;
        this.description = description;
    }

}

Basicallu I need to find a smart way (maybe using lambda function?) to check if into the Set returned by the getUserTypes() there is a UserType object having the typeName field equals to the SUB-AGENT string.

How can I correctly and nicely implement this behavior?

Answer 1

You can use anyMatch for this. It is a terminal operation on the stream which returns true if the passed predicate (condition) evaluates to true for at least one element (UserType instance). It is a short-circuiting operation.

boolean hasTypeName = retrievedUser.get().getUserTypes()
    .stream()
    .anyMatch(userType -> userType.getTypeName.equals("SUB-AGENT")
if (hasTypeName) {...}

or inline it as

if (retrievedUser.get().getUserTypes()
    .stream()
    .anyMatch(userType -> userType.getTypeName.equals("SUB-AGENT")) {...}