Member Avatar for kukuruku

Is it OK to have if statement in the constructor
Thanks

public class CTime {
  private int start_hour;
  private int end_hour;
  private int start_minute;
  private int end_minute;
  public CTime(int h1,int m1,int h2,int m2){
	  if(h1>=7 && h2<17 && h2*60+m2>h1*60+m1){
	  setStartHour(h1);
	  setStartMinute(m1);
	  setEndHour(h2);
	  setEndMinute(m2);
	  }
	   
  }
  • 4 Contributors
  • 9 Replies
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  • 12 Years Discussion Span
  • Latest Post Latest Post by Washington AM

Dani AI

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Yes, you can use conditionals in a constructor; just ensure the class invariants are either fully established or the constructor throws. In Java, constructors are not regular methods; they are special routines that initialize an object. For invalid arguments, prefer throwing unchecked exceptions like IllegalArgumentException or NullPointerException (not a generic Exception) so callers immediately see misuse. For reference parameters, use Objects.requireNonNull, and avoid calling mutating setters from inside constructors; validate first, then assign to fields (ideally final) to avoid partially constructed state. See the Oracle docs on constructors (link), IllegalArgumentException (link), and Objects.requireNonNull (link).

For time validation, consider java.time. It gives clearer, bug-resistant checks for ranges and ordering:

import java.time.LocalTime;

public final class CTime {
  private final LocalTime start;
  private final LocalTime end;

  public CTime(int h1, int m1, int h2, int m2) {
    LocalTime s = LocalTime.of(h1, m1); // throws if out of range
    LocalTime e = LocalTime.of(h2, m2);

    if (s.isBefore(LocalTime.of(7, 0)) ||
        !e.isBefore(LocalTime.of(17, 0)) ||
        !e.isAfter(s)) {
      throw new IllegalArgumentException("Start >= 07:00, end < 17:00, and end after start.");
    }
    this.start = s;
    this.end = e;
  }
}

For mixed types like int and String, validate primitives explicitly (e.g., age > 0) and require non-null references: this.name = Objects.requireNonNull(name, "name");. The java.time API is documented here: link.

Recommended Answers

All 9 Replies

Member Avatar for JamesCherrill

Yes. Just make sure that the new Object is has all its variables in a decent state regardless of which conditional paths are executed.

Member Avatar for amrita111

Constructor is a method.You can have if statement in a constructor

Member Avatar for kukuruku

Thanks ,another question is there method witch is checking if the object arguments are different then null.

obj people(age,name,gender)

Member Avatar for JamesCherrill

Do you mean like

if (age != null) ...

but you can only do this for reference types (objects), things like ints or floats can't be null anyway.

Member Avatar for kukuruku

Thanks,I meant to check int!=0 && String!=null
in the same object

Member Avatar for JamesCherrill

Yes, you can do exactly that.
The more interesting question is what will you do if you find invalid parameters in a constructor? How will the calling method know that its new Person(0, "Who?", 'X'); statement wasn't executed as it expected?
One option is to declare the constructor as throws (some kind of exception) and throw a new Exception if the params are invalid.

Member Avatar for kukuruku

Thanks,could you give example with code how to do that

Member Avatar for JamesCherrill 
public Person(int age) throws Exception {
  if (age <= 0) throw new Exception("Age must be positive");
  this.age = age;
  (etc)
}
Member Avatar for Washington AM

I am asking for solution of this program please.

Edited by rproffitt because: Please start a new discussion. Avoid unsafe attachments.
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