Java: How can a constructor return a value? [duplicate]

Answer 1

I think the best way to produce the effect you want would be the following:

public class Const {

    private String str;

    public Const(String hello) {
        str = hello; 
    }

    public String toString() {
        return str;
    }

    public static void main(String[] args) {
        System.out.println(new Const("Hello!"));
    }
}

This replaces the public String Const() method you used previously, and by overriding the public String toString() method of Object (Which all Java classes inherit from) the String value of the object is printed correctly when you want to print the object, so your main method remains unchanged.

Answer 2

A constructor can not return a value because a constructor implicitly returns the reference ID of an object, and since a constructor is also a method and a method can't return more than one values. So we say explicitely constructor does not have a return value.

Answer 3

public class Const {
  private String myVar;

  public Const(String s) {
    myVar = s; 
  }

  public String getMyString()
  {
      return myVar;
  }

  public static void main(String[] args) {
    Const myConst = new Const("MyStringHere"); 
    System.out.println(myConst.getMyString());
  }
}

Answer 4

To pass back a value from a constructor - just pass in an array as a parameter. To illustrate the principle:

Test() {
    Boolean[] flag = new Boolean[1];
    flag[0] = false;
    new MyClass(flag);
    System.out.println(flag[0]); // Will output 'true'
}

class MyClass {
    MyClass(Boolean[] flag) {
        // Do some work here, then set flag[0] to show the status
        flag[0] = true;
    }
}

Answer 5

/************************************************
   Put the return value as a private data member, which gets
   set in the constructor. You will need a public getter to
   retrieve the return value post construction
******************************************************/

class MyClass
{
   private Boolean boolReturnVal;

   public Boolean GetReturnVal() { return(boolReturnVal); }
   MyClass() // constructor with possibly args
    {
       //sets the return value boolReturnVal
    }

 public static void main(String args[])
 {
     MyClass myClass = new MyClass();

    if (myClass.GetReturnVal())
    {
       //success
    }

 }

}

Answer 6

The constructor cannot return a value. That's final. It the same sense - it cannot have a return type and that's why you're getting the compile error. You may say that the return value is always implicitly the object created by the constructor.