java类型强转为泛型V，竟然没有报错？报错

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public class StrictMap<V> extends HashMap<String, V> {

private static final long serialVersionUID = -3455861209780003757L;

private String name;

public StrictMap(int initialCapacity, float loadFactor, String name) {
    super(initialCapacity, loadFactor);
    this.name = name;
}

public StrictMap(int initialCapacity, String name) {
    super(initialCapacity);
    this.name = name;
}

public StrictMap(String name) {
    this.name = name;
}

public String getName() {
    return name;
}

public void setName(String name) {
    this.name = name;
}

@Override
public V put(String key, V value) {
    if (containsKey(key)) {
        throw new RuntimeException("已经存在的key, keyName = " + key);
    }

    if (key.contains(".")) {
        final String shortName = getShortName(key);
        if (containsKey(shortName)) {
            // question 这边有个问题， 为什么没有抛出ClassCastException。
            V ambiguity = (V) new Ambiguity("存在的shortName");
            super.put(shortName, ambiguity);
        } else {
            super.put(shortName, value);
        }
    }

    return super.put(key, value);
}

@Override
public V get(Object key) {
    V value = super.get(key);
    if (value == null) {
        throw new RuntimeException("keyName = " + key + ", 没有获取到value.");
    }
    if (value instanceof Ambiguity) {
        throw new RuntimeException("重复的shortName");
    }
    return value;
}

static class Ambiguity {
    private String name;

    public Ambiguity(String name) {
        this.name = name;
    }

    public String getName() {
        return name;
    }
}

}

ps:运行时也没报错。