In Java, we're used to having overloaded constructors:

class MyClass {
    private final String a;
    private final Integer b;
    public MyClass(String a) {
        this(a, 1);
    }

    public MyClass(String a, Integer b) {
        this.a = a;
        this.b = b;
    }
}

We can simulate the same behavior in Kotlin:

class MyClass(val a: String, val b: Int, val c: Long) {
    
    constructor(a: String, b: Int) : this(a, b, 0) 
    
    constructor(a: String) : this(a, 1)
    
    constructor() : this("Default")
}

But it's usually better to have default parameter values and named arguments instead:

class BetterClass(val a: String = "Default",
                  val b: Int = 1,
                  val c: Long = 0)