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最新推荐文章于 2024-07-19 15:49:26 发布

xjk201

最新推荐文章于 2024-07-19 15:49:26 发布

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本文链接：https://blog.youkuaiyun.com/xjk201/article/details/80974398

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本文通过Java代码示例介绍了多态性和运行时类型识别(RTTI)的概念。展示了如何使用多态调用方法，并通过强制类型转换实现特定子类的方法调用。同时，也说明了RTTI可能导致的ClassCastException异常。

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class Cycle {
private String name = "Cycle";
public static void travel(Cycle c) {
println("Cycle.ride() " + c);
}
public String toString() {
return this.name;
}
}

class Unicycle extends Cycle {
private String name = "Unicycle";
public void balance() { println("Balance Unicycle"); }
public String toString() {
return this.name;
}
}

class Bicycle extends Cycle {
private String name = "Bicycle";
public void balance() { println("Balance Bicycle"); }
public String toString() {
return this.name;
}

}

class Tricycle extends Cycle {
private String name = "Tricycle";
public String toString() {
return this.name;
}
}

public class Biking17 {
public static void main(String[] args) {
  Cycle[] ride = {
   new Unicycle(),
   new Bicycle(),
   new Tricycle(),
  };
  // Compile time error: cannot find balance() method in Cycle:
  // for(Cycle c : ride) {
  // c.balance();
  // }
  ((Unicycle)ride[0]).balance();
  ((Bicycle)ride[1]).balance();
  // Compile time error: no balance() in Tricycle:
  // ((Tricycle)ride[2]).balance();
  // RTTI: ClassCastException: Tricycle cannot be cast to Bicycle:
  // ((Bicycle)ride[2]).balance();
}
}

输出：