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class Singleton { 
    private volatile static Singleton object; 
  
    private Singleton() {} 
  
    public static Singleton getInstance() { 
        if (object == null) { 
            synchronized (Singleton.class) { 
               if (object == null) 
                    object = new Singleton(); 

bhawna94

class Singleton {

   // Creating an Instance
    private static Singleton object = new Singleton(); 
  
    private Singleton() {} 
  
    public static Singleton getInstance() { 
        return object; 
    } 

bhawna94

class Singleton { 
  
  //static field
  private static Singleton object; 
    
  //private Construtor
  private Singleton() {} 
  
  //static method
  public static synchronized Singleton getInstance() 

bhawna94

class Singleton { 
  
  //static field
  private static Singleton object; 
    
  //private Construtor
  private Singleton() {} 
  
  //static method
  public static Singleton getInstance() 

bhawna94

import com.knoldus.wallet.model.StudentInfo;
import com.knoldus.wallet.repository.StudentRepository;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.http.HttpStatus;
import org.springframework.web.bind.annotation.DeleteMapping;
import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.PathVariable;
import org.springframework.web.bind.annotation.PostMapping;
import org.springframework.web.bind.annotation.RequestBody;
import org.springframework.web.bind.annotation.RestController;

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import org.springframework.data.jpa.repository.JpaRepository;
import org.springframework.stereotype.Repository;

@Repository
public interface StudentRepository extends JpaRepository<StudentInfo, String> {

//We can add our derivable query also.    
}

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spring.datasource.url=jdbc:mysql://localhost:3306/database_name
spring.datasource.username=root
spring.datasource.password=root

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import lombok.AllArgsConstructor;
import lombok.Builder;
import lombok.Getter;
import lombok.NoArgsConstructor;
import lombok.Setter;

import javax.persistence.Column;
import javax.persistence.Entity;
import javax.persistence.Id;
import javax.persistence.Table;

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 <!-- jpa,repository -->
    <dependency>
       <groupId>org.springframework.boot</groupId>
       <artifactId>spring-boot-starter-data-jpa</artifactId>
        </dependency>
        
<!-- MySQL -->
        <dependency>
            <groupId>mysql</groupId>
            <artifactId>mysql-connector-java</artifactId>

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 // find the document by Id and mapped to the corresponding POJO
Employee emp = couchbaseTemplate.findById("id", Employee.class);