Hiding a constructor behind a static creator method?

Question

I\'ve recently discovered an interesting way to create a new instance of an object in Google Guava and Project Lombok: Hide a constructor behind a static creator method. Thi

Answer 1

Unlike constructors, static methods can have method names. Here's a recent class I wrote where this was useful:

/**
 * A number range that can be min-constrained, max-constrained, 
 * both-constrained or unconstrained.
 */

public class Range {
  private final long min;
  private final long max;
  private final boolean hasMin;
  private final boolean hasMax;

  private Range(long min, long max, boolean hasMin, boolean hasMax) {
    // ... (private constructor that just assigns attributes)
  }

  // Static factory methods

  public static Range atLeast (long min) {
    return new Range(min, 0, true, false);
  }

  public static Range atMost (long max) {
    return new Range(0, max, false, true);
  }

  public static Range between (long min, long max) {
    return new Range(min, max, true, true);
  }

  public static Range unconstrained () {
    return new Range (0, 0, false, false);
  }
}

You couldn't do this using just constructors, as atLeast and atMost would have the exact same signature (they both take one long).