Implementation of clone method for Java Record

Implement the clone method in Record which is the 2nd preview in Java 15 so that you can make a deep copy. I don't think there is a particular scene to use this, but I may use it someday, so I'll use it as a memorandum. The point is to make a clone in the constructor without using super.clone ().

environment

Java 15（Oracle Open JDK） IntelliJ IDEA Community Edition Windows

• Refer to the following for the settings for using Record with IntelliJ (although it is miso in the foreground). https://qiita.com/tora_kouno/items/58eff9f4eb99a941fd41

Implementation

Before implementing clone

ExampleRecord.java

public record ExampleRecord(String name, int age, ExampleDto dto) {
}

ExampleDto.java

public class ExampleDto {
  private String name;
  private int age;
  private NodeDto node;
  // setter, getter,toString omitted
}

NodeDto.java

public class NodeDto {
  private String name;
  // setter, getter,toString omitted
}

After implementing clone

ExampleRecord.java

public record ExampleRecord(String name, int age, ExampleDto dto) {
  @Override
  public ExampleRecord clone() {
    try {
      return new ExampleRecord(this.name, this.age, this.dto.clone());
    } catch (CloneNotSupportedException e) {
      e.printStackTrace();
    }
    return null;
  }
}

ExampleDto.java

public class ExampleDto implements Cloneable {
  private String name;
  private int age;
  private NodeDto node;
  // setter, getter,toString omitted

  @Override
  public ExampleDto clone() throws CloneNotSupportedException {
    ExampleDto copy = (ExampleDto) super.clone();
    copy.node = this.node.clone();
    return copy;
  }
}

NodeDto.java

public class NodeDto implements Cloneable {
  private String name;
  // setter, getter,toString omitted

  @Override
  public NodeDto clone() throws CloneNotSupportedException {
    return (NodeDto) super.clone();
  }
}

try

Implementation

Main.java

public class Main {
  public static void main(String[] args) {
    ExampleDto dto = new ExampleDto();
    NodeDto nodeDto = new NodeDto();
    nodeDto.setName("node1");
    dto.setNode(nodeDto);
    dto.setName("dto1");
    dto.setAge(1);
    ExampleRecord exampleRecord = new ExampleRecord("record1", 2, dto);
    System.out.println("exampleRecord:"+exampleRecord);// 1
    dto.setName("dto2");
    nodeDto.setName("node2");
    System.out.println("exampleRecord:"+exampleRecord);// 2

    ExampleRecord clone = exampleRecord.clone();
    System.out.println("clone:"+clone);// 3
    dto.setName("dto3");
    nodeDto.setName("node3");
    System.out.println("clone:"+clone);// 4
  }
}

Execution result

1.

exampleRecord:ExampleRecord[name=record1, age=2, dto=ExampleDto{name='dto1', age=1, node=NodeDto{name='node1'}}]

2.

exampleRecord:ExampleRecord[name=record1, age=2, dto=ExampleDto{name='dto2', age=1, node=NodeDto{name='node2'}}]

3.

clone:ExampleRecord[name=record1, age=2, dto=ExampleDto{name='dto2', age=1, node=NodeDto{name='node2'}}]

4.

clone:ExampleRecord[name=record1, age=2, dto=ExampleDto{name='dto2', age=1, node=NodeDto{name='node2'}}]

In 1-> 2, the contents of Dto have changed, but in 3-> 4, it is a different instance, so dto.setName ("dto3"); andnodeDto.setName ("node3"); You can see that it is unaffected and cloned without any problems.