Java 如何从 LinkedHashMap 迭代器获取键值对？
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How I can get key, value pair from LinkedHashMap iterator?
提问by Borneq
I test SnakeYAML library to read .yaml documents. I have read Example 2.27. Invoice from http://yaml.org/spec/1.1/and I get object:
我测试 SnakeYAML 库以读取 .yaml 文档。我已经阅读了示例 2.27。来自http://yaml.org/spec/1.1/ 的发票，我得到了对象：
System.out.println(content);
Yaml yaml = new Yaml();
Object o = yaml.load(content);
where content is String loaded from file using Files.readAllBytes, encoding.decode (encoding is StandardCharsets.UTF_8)
其中内容是使用 Files.readAllBytes, encoding.decode 从文件加载的字符串（编码是 StandardCharsets.UTF_8）
Reflection gaves me that o is type of java.util.LinkedHashMap and I can iterate over them:
反射告诉我 o 是 java.util.LinkedHashMap 的类型，我可以遍历它们：
Set entrySet = o.entrySet();
Iterator it = entrySet.iterator();
System.out.println("LinkedHashMap entries : ");
while (it.hasNext())
{
Object entry = it.next();
System.out.println(entry);
}
Reflection return that type of entry is LinkedHashMap$Entry. But is problem: internal class LinkedHashMap$Entry is private and I can't declare objects this type. How I can get pair from entry, iterator or entrSet?
反射返回该条目类型为 LinkedHashMap$Entry。但问题是：内部类 LinkedHashMap$Entry 是私有的，我不能声明这种类型的对象。我如何从条目、迭代器或 entrSet 中获取配对？
回答by Boris the Spider
You should declare a Map.Entryrather than the LinkedHashMap.Entry:
您应该声明 aMap.Entry而不是LinkedHashMap.Entry：
while (it.hasNext())
{
Map.Entry<?,?> entry = it.next();
System.out.println(entry.getKey());
System.out.println(entry.getValue());
}
Map.Entryis the public interface, LinkedHashMap.Entryis a private implementation of that interface.
Map.Entry是public interface,LinkedHashMap.Entry是该接口的私有实现。
Notice that I also declare the Entrywith <?,?>, this is a generic declaration. If you know the type of the Mapyou can declare that type and you won't need to cast:
请注意，我还声明了Entrywith <?,?>，这是一个通用声明。如果您知道 的类型，则Map可以声明该类型并且不需要强制转换：
Set<Entry<?,?>> entrySet = o.entrySet();
Iterator<Entry<?,?>> it = entrySet.iterator();
Further you can use an enhanced foreach loop to iterate:
此外，您可以使用增强的 foreach 循环进行迭代：
final Map<?,?> myMap = (Map<?,?>) yaml.load(content);
for(final Entry<?,?> entry : o.entrySet()) {
//do stuff with entry
}
Obviously if you know your Mapis mapping Stringto Object(for example) you could use Map<String, Object>
显然，如果您知道您Map要映射String到Object（例如），您可以使用Map<String, Object>
回答by Trey Jonn
Check out the examples posted at: Java - The LinkedHashMap Classand How do I get a keyIterator for a LinkedHashMap?
查看发布在以下位置的示例： Java - LinkedHashMap 类和 如何获取 LinkedHashMap 的 keyIterator？
