使用HashMap的潜在资源泄漏(未分配Closeable) [英] potential resource leak (unassigned Closeable) with a HashMap

问题描述

我在整个系统中都有一个静态HashMap，其中包含一些对象的引用；我们称之为myHash.这些对象仅在我需要它们时被实例化，例如

I have one static HashMap for my entire system which contains some object's references; let's call it myHash. The objects are only instantiated once I needed them such as

private static HashMap<String, lucene.store.Directory> directories;

public static Object getFoo(String key) {
    if (directories == null) {
        directories = new HashMap<String, Directory>();
    }
    if (directories.get(key) == null) {
        directories.put(key, new RAMDirectory());
    }
    return directories.get(key); // warning
}

现在，Eclipse在return语句中告诉我一个警告:

Now, Eclipse is telling me a warning in the return statement:

Potential resource leak: '<unassigned Closeable value>' may not be closed at this location

为什么月食会告诉我?

推荐答案

Directory是一个Closeable，它没有使用实例化的相同方法被关闭，Eclipse警告您，如果不关闭它，可能会造成潜在的资源泄漏别的地方.换句话说，Closeable实例应该始终在某个位置关闭，无论可能引发什么错误.

Directory is a Closeable that is not closed in the same method it is instantiated in, Eclipse warns you this could create potential resource leaks if not closed somewhere else. In other words, a Closeable instance should always be closed somewhere, whatever error could have been thrown.

这是在Java 7+中使用Closeable的常用方法:

Here is the usual way to use a Closeable in Java 7+:

try (Directory dir = new RAMDirectory()) {
    // use dir here, it will be automatically closed at the end of this block.
}
// exception catching omitted

在Java 6-中:

Directory dir = null;
try {
    dir = new RAMDirectory();
    // use dir here, it will be automatically closed in the finally block.
} finally {
    if (dir != null) {
        dir.close(); // exception catching omitted
    }
}

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