Class IntegerSingleton

patterns/SingletonPattern.java:6–21

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final class IntegerSingleton
  implements Resource<Integer> {
  private static IntegerSingleton value =
    new IntegerSingleton();
  private Integer i = Integer.valueOf(0);
  private IntegerSingleton() {
    System.out.println("IntegerSingleton()");
  }
  public static IntegerSingleton instance() {
    return value;
  }
  @Override public synchronized
  Integer get() { return i; }
  @Override public synchronized
  void set(Integer x) { i = x; }
}

public class SingletonPattern {
  public static <T> void show(Resource<T> r) {