applesandorangeswithoutgenerics.java

来自「Thinking in JAVA第四版源代码」· Java 代码 · 共 27 行

//: holding/ApplesAndOrangesWithoutGenerics.java
// Simple container example (produces compiler warnings).
// {ThrowsException}
import java.util.*;

class Apple {
  private static long counter;
  private final long id = counter++;
  public long id() { return id; }
}

class Orange {}	

public class ApplesAndOrangesWithoutGenerics {
  @SuppressWarnings("unchecked")
  public static void main(String[] args) {
    ArrayList apples = new ArrayList();
    for(int i = 0; i < 3; i++)
      apples.add(new Apple());
    // Not prevented from adding an Orange to apples:
    apples.add(new Orange());
    for(int i = 0; i < apples.size(); i++)
      ((Apple)apples.get(i)).id();
      // Orange is detected only at run time
  }
} /* (Execute to see output) *///:~