data class in kotlin demo - auto implemented equals(), hashcode(), and toString() methods. special function copy() make new reference or new object when data modified

dataClassDemo.kt

fun main() {
    val emp1 = Employee(name = "audhil", id = 33)
    val emp2 = Employee(name = "audhil", id = 33)

    if (emp1 == emp2) {
        println("equal")
    } else
        println("not equal")

    println(emp1.hashCode())
    println(emp2.hashCode())

    val emp3 = emp1.copy()
    println("emp3:")
    println(emp3)
    println(emp3.hashCode())

    val emp4 = emp1.copy(id = 33)
    println("emp4:")
    println(emp4)
    println(emp4.hashCode())

    val emp5 = emp1.copy(id = 3)
    println("emp5:")
    println(emp5)
    println(emp5.hashCode())
    
    /*
    * o/p
    * equal
        -661290842
        -661290842
        emp3:
        Employee(name=audhil, id=33)
        -661290842
        emp4:
        Employee(name=audhil, id=33)
        -661290842
        emp5:
        Employee(name=audhil, id=3)
        -661290872
    * */
}

data class Employee(
    val name: String,
    val id: Int
)

withAnotherClassRef.kt

fun main() {
    val emp1 = Employee(name = "audhil", id = 33, company = Company("zoho"))
    val emp2 = Employee(name = "audhil", id = 33, company = Company("logica"))

    println(emp1)
    println(emp1.hashCode())
    println(emp2)
    println(emp2.hashCode())
    if (emp1 == emp2) {
        println("yup equals")
    } else
        println("yup not equals")

    val emp3 = emp1.copy()
    println(emp3)
    println(emp3.hashCode())

    val emp4 = emp1.copy(id = 11)
    println(emp4)
    println(emp4.hashCode())

    val emp5 = emp1.copy(company = Company("zam zam"))
    println(emp5)
    println(emp5.hashCode())
    
    /*
    * o/p
    * 
    * emp1:
        Employee(name=audhil, id=33, company=Company(companyName=zoho))
        978564886
        emp2:
        Employee(name=audhil, id=33, company=Company(companyName=logica))
        -122515235
        yup not equals
        emp3:
        Employee(name=audhil, id=33, company=Company(companyName=zoho))
        978564886
        emp4:
        Employee(name=audhil, id=11, company=Company(companyName=zoho))
        978564204
        emp5:
        Employee(name=audhil, id=33, company=Company(companyName=zam zam))
        459884870
    * 
    * */
}

data class Employee(
    val name: String,
    val id: Int,
    val company: Company
)

data class Company(
    val companyName: String
)

withCollections.kt

package _00WarmUp

fun main() {
    val emp1 = Employee(name = "audhil", id = 33, company = Company("zoho"), tokenList = listOf(Token(1), Token(30)))

    println("emp1:")
    println(emp1)
    println(emp1.hashCode())

    val emp2 = emp1.copy()
    println("emp2:")
    println(emp2)
    println(emp2.hashCode())

    val emp3 = emp1.copy(id = 11)
    println("emp3:")
    println(emp3)
    println(emp3.hashCode())
    
    /*
    * o/p
    * 
    * emp1:
        Employee(name=audhil, id=33, company=Company(companyName=zoho), tokenList=[Token(tokenNo=1), Token(tokenNo=30)])
        270741416
        emp2:
        Employee(name=audhil, id=33, company=Company(companyName=zoho), tokenList=[Token(tokenNo=1), Token(tokenNo=30)])
        270741416
        emp3:
        Employee(name=audhil, id=11, company=Company(companyName=zoho), tokenList=[Token(tokenNo=1), Token(tokenNo=30)])
        270720274
    * 
    * */
}

data class Employee(
    val name: String,
    val id: Int,
    val company: Company,
    val tokenList: List<Token>
)

data class Company(
    val companyName: String
)

data class Token(
    val tokenNo: Int
)