サンプルはカウンタ -- Java版

前のエントリのJavaScriptサンプルに対応するJavaコードです。

/* Counter.java */
public class Counter {

 public static final int UPPER_BOUND = 10;

 public static final int MAX_COUNTERS = 3;

 public static int counters = 0;
 public int value;
 public Counter(int initValue) {

  if (counters >= MAX_COUNTERS) {

   throw new RuntimeException("too many counters.");

  }

  if (0 <= initValue && initValue < UPPER_BOUND) {

   value = initValue;

  } else {

   throw new RuntimeException("Illegal initial value:" + initValue);

  }

  counters++;

 }

 public Counter() {

  this(0);

 }
 public void inc() {

  if (value + 1 >= UPPER_BOUND) {

   throw new RuntimeException("counter overflow.");

  }

  value++;

 }

 public void dec() {

  if (value <= 0) {

   throw new RuntimeException("counter underflow.");

  }

  value--;

 }

}