@Entity
@Table(name = "QBMS_BANK")
public class QuestionBank extends BaseEntity {

    private static final long serialVersionUID = 8276628395037978969L;

    @Column(name = "NAME", unique = true)
    @Size(max = 100)
    @NotNull
    private String name;

    @OneToMany(mappedBy = "bank", fetch = FetchType.LAZY, cascade = CascadeType.ALL, orphanRemoval = true)
    @MapKey(name = "user")
    private Map<User, QuestionBankUserPermission> userPermissions;

    public String getName() {
        return name;
    }

    public Map<User, QuestionBankUserPermission> getUserPermissions() {
        return userPermissions;
    }

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

    public void setUserPermissions(
            Map<User, QuestionBankUserPermission> userPermissions) {
        this.userPermissions = userPermissions;
    }
}

QuestionBankUserPermission userPermission = bank
                    .getUserPermissions().get(user);
            System.err.println("userPermission->" + userPermission);

if(bank.getUserPermissions().containsKey(user)){
                System.err.println("yes");
            }

for (Map.Entry<User, QuestionBankUserPermission> entry : bank
                    .getUserPermissions().entrySet()) {
                if (entry.getKey().equals(user)) {
                    System.err.println("existed the same key");
                }
            }