Java Basics - Record

 Record is one of the cool features Java has and below are the difference with normal class Vs Record class and how it will help us to get rid of boilerplate code.

For understanding purpose, we create a simple class with two variables, name and email.

you can see how much code we need to write in legacy class to deal with just to deal with a record/object with two variables

• two variables
• Getters and setter
• Constructor
• equals and hashcode
• toString() Method

In Record

    just the class name with variables inside parenthesis

Record

variables are final - so no setters

Record will create a canonocal constructor - with parametrs you have given, where in class it will create only default constructor without paramters

Can have instance methods.

Can have static methods

Static variables, cannot create instance variables - why , by default, Record is a final

Get the value of variables using the name and paranthesis eg:varibaleName()

Record has by default toString method

Cannot extend any class cause By default it extends Record class, But you can implement any interface

Has a compact constructor

Can have validations here

name of the record is enough to declare constructor with "public" access

eg: 

public record SampleRecord(String name, String email) {

 public SampleRecord {
        if (name.isBlank()) {
            throw new IllegalArgumentException("Name cannot be blank.");
        }
    }

}

Below are sample code blocks

package com.example.demo.records;

import java.util.Objects;

public class SampleClass {
    private String name;
    private String email;

    public SampleClass(String name, String email) {
        this.name = name;
        this.email = email;
    }

    public String getName() {
        return name;
    }

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

    public String getEmail() {
        return email;
    }

    public void setEmail(String email) {
        this.email = email;
    }

    @Override
    public String toString() {
        return "SampleClass{" +
                "name='" + name + '\'' +
                ", email='" + email + '\'' +
                '}';
    }

    @Override
    public boolean equals(Object o) {
        if (this == o) return true;
        if (o == null || getClass() != o.getClass()) return false;
        SampleClass that = (SampleClass) o;
        return name.equals(that.name) && email.equals(that.email);
    }

    @Override
    public int hashCode() {
        return Objects.hash(name, email);
    }
}

package com.example.demo.records;

public record SampleRecord(String name, String email) {

    public static String STATIC_VARIABLE = "static_variable";
    // Instance variables are not allowed as by default variables are final cause of Record
    //public String instanceVarible ="instanceVairableNot Allowed";
    public String instanceMethod() {
        return name();
    }

    public static void staticMethod() {
        System.out.println("From static method");
    }


    public SampleRecord {
        if (name.isBlank()) {
            throw new IllegalArgumentException("Name cannot be blank.");
        }
    }

}

package com.example.demo.records;

public class TestSampleRecord {
    public static void main(String[] args) {
        SampleClass sampleClass = new SampleClass("Roshan", "roshan@email.com");
        System.out.println(sampleClass);

        SampleRecord sampleRecord = new SampleRecord("Mahanama", "mahanama@email.com");
        System.out.println("default toString method in Record");
        System.out.println(sampleRecord);
        System.out.println("From instance method :" + sampleRecord.instanceMethod());
        SampleRecord.staticMethod();
        System.out.println(new SampleRecord("", ""));
    }
}

 Output

SampleClass{name='Roshan', email='roshan@email.com'}

default toString method in Record

SampleRecord[name=Mahanama, email=mahanama@email.com]

From instance method :Mahanama

From static method

Exception in thread "main" java.lang.IllegalArgumentException: Name cannot be blank.

at com.example.demo.records.SampleRecord.<init>(SampleRecord.java:16)

at com.example.demo.records.TestSampleRecord.main(TestSampleRecord.java:13)