使用Java 8 update101时，HashMap.entries无法强制转换为Collection [英] With Java 8 update101 HashMap.entries cannot be cast to Collection

问题描述

更新到Java 8更新101后，我在以下代码中遇到异常。它与Java 8更新91一起工作正常。

After updating to Java 8 update 101, I am getting exception in following code. It was working fine with Java 8 update 91.

访问密钥库：

        KeyStore ks = KeyStore.getInstance("WINDOWS-MY");
        ks.load(null, null);

        Field field =  ks.getClass().getDeclaredField("keyStoreSpi");
        field.setAccessible(true);

        KeyStoreSpi kss = (KeyStoreSpi) field.get(ks);

        Collection entries;

        field = kss.getClass().getEnclosingClass().getDeclaredField("entries");
        field.setAccessible(true);

        // This is where the exception happens
        entries = (Collection) field.get(kss);

        // I then have to loop on these entries, something like this:

        for (Object entry : entries) { //code }

类型转换，抛出异常：

java.util.HashMap cannot be cast to java.util.Collection

最近的任何更改Java 8更新101？如何解决？

Any recent changes in Java 8 update 101? How to solve it?

推荐答案

我确认使用以下代码作为测试代码不起作用

I confirm it does not work using the following as test code

import java.util.HashMap;
import java.util.Collection;

public class HelloWorld {
   public static void main(String[] args) {
      HashMap map = new HashMap();
      Collection c;
      c = (Collection) map;
   }
}

结果是线程中的异常main java.lang.ClassCastException：java.util.HashMap无法在HelloWorld.main（HelloWorld.java:8）上转换为java.util.Collection

您可以使用像这样的values（）方法覆盖它

You can override it by using the values() method like this

import java.util.HashMap;
import java.util.Collection;

public class HelloWorld {
   public static void main(String[] args) {
      HashMap map = new HashMap();
      Collection c;
      c = map.values();
   }
}

所以你的代码应该是这样的

So your code should be like this

import java.util.HashMap;
import java.util.Collection;
import java.security.*;
import java.lang.reflect.Field;

public class HelloWorld {
   public static void main(String[] args) {
    try{
      KeyStore ks = KeyStore.getInstance("WINDOWS-MY");
        ks.load(null, null);

        Field field =  ks.getClass().getDeclaredField("keyStoreSpi");
        field.setAccessible(true);

        KeyStoreSpi kss = (KeyStoreSpi) field.get(ks);

        Collection entries;

        field =kss.getClass().getEnclosingClass().getDeclaredField("entries");
        field.setAccessible(true);
        entries = ((HashMap) field.get(kss)).values();
    }catch(Exception e){
        e.printStackTrace();
    }
   }
}

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