java - 如何使用可变参数和反射

Question

简单的问题，如何使这段代码工作？

public class T {

    public static void main(String[] args) throws Exception {
        new T().m();
    }

    public // as mentioned by Bozho
    void foo(String... s) {
        System.err.println(s[0]);
    }

    void m() throws Exception {
        String[] a = new String[]{"hello", "kitty"};
        System.err.println(a.getClass());
        Method m = getClass().getMethod("foo", a.getClass());
        m.invoke(this, (Object[]) a);
    }
}

输出:

class [Ljava.lang.String;
Exception in thread "main" java.lang.IllegalArgumentException: wrong number of arguments
        at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
        at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:39)
        at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)
        at java.lang.reflect.Method.invoke(Method.java:597)

Answer 1

Test.class.getDeclaredMethod("foo", String[].class);

有效。问题是 getMethod(..) 只搜索 public 方法。来自 javadoc:

Returns a Method object that reflects the specified public member method of the class or interface represented by this Class object.

更新:成功获取方法后，可以使用:

m.invoke(this, new Object[] {new String[] {"a", "s", "d"}});

即 - 创建一个新的 Object 数组，其中包含一个元素 - String 数组。使用您的变量名称，它看起来像:

m.invoke(this, new Object[] {a});