对类使用泛型类型

public class Box<T> {
    private T value;

    public Box(T value) {
        this.value = value;
    }

    public T getValue() {
        return value;
    }

    public void setValue(T value) {
        this.value = value;
    }
}

Box<Integer> intBox = new Box<>(123);
System.out.println(intBox.getValue()); // 输出: 123

Box<String> strBox = new Box<>("Hello");
System.out.println(strBox.getValue()); // 输出: Hello

public class GenericClass<T> {
    private Class<T> clazz;

    public GenericClass(Class<T> clazz) {
        this.clazz = clazz;
    }

    public T createInstance() throws Exception {
        return clazz.newInstance();
    }
}

public static void printList(List<? extends Number> list) {
    for (Number num : list) {
        System.out.println(num);
    }
}