Red > Green > Refactor > Red

cycle is based on desire

static field initiate optimize

src
 |
 + -- jp.ymatsukawa
           |
           + -- constructor
           |         |
           |         + -- InstanceAble.java
           + -- Main.java           

jp.ymatsukawa/Main.java

package jp.ymatsukawa;

import jp.ymatsukawa.constructor.InstantiateAble;
import java.util.Calendar;

public class Main {
  public static void main(String[] args) {
    InstantiateAble instantiateAble = new InstantiateAble();
  }
}

jp.ymatsukawa/constructor/InstantiateAble.java

package jp.ymatsukawa.constructor;

public class InstantiateAble {
  private int someIntValue;
  private static int classConstantX;
  private static int classConstantY;
  static {
    // instantiate static field
    //   only the first time the class instantiated
    classConstantX = 80;
    classConstantY = 5;
  }
  public InstantiateAble() {
    // when called constructor, static field is already instantiated upon
    this.someIntValue = (classConstantX + classConstantY);
  }
}

when use constant value, consider also utility class