java.io.Reader的java.lang.NullPointerException。在java.io.InputStreamReader中的<init>（Reader.java:78）。<init>（InputStreamReader.java:72）

Question

有时使用下面的代码片段获取NullPointerException的原因是什么。

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Exception in thread "main" java.lang.NullPointerException
     [java] 	at java.io.Reader.<init>(Reader.java:78)
     [java] 	at java.io.InputStreamReader.<init>(InputStreamReader.java:72)
     [java] 	at helloworld.HelloWorld.fixture(Unknown Source)
     [java] 	at helloworld.HelloWorld.replaceScheduler(Unknown Source)
     [java] 	at helloworld.HelloWorld.test(Unknown Source)
     [java] 	at helloworld.HelloWorld.main(Unknown Source)

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我的代码我试图读取该文件扩展名.fscript;问题是getResourceAsStream（name）返回null

以下是所有代码：

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public class HelloWorld {
    FScriptInterpreter fscript;
    Node rootNode; 
    
    private Reader fixture(String name) {
        InputStream stream = HelloWorld.class.getClassLoader().getResourceAsStream(name);
        return new InputStreamReader(stream);
    } 
    
	private Component getChildByName(Component parent, String name)
            throws NoSuchInterfaceException {
        ContentController cc = Fractal.getContentController(parent);
        for (Component child : cc.getFcSubComponents()) {
            if (name.equals(Fractal.getNameController(child).getFcName())) {
                return child;
            }
        }
        return null;
    }
	
	public void replaceScheduler(Component root) throws Exception {
        Component client = getChildByName(root, "client");
        fscript.loadDefinitions(fixture("replace-scheduler.fscript"));
        fscript.apply("replace-scheduler", new Object[] { rootNode });
        Component newScheduler = getChildByName(client, "client1");
        assertNotNull("New scheduler not found.", newScheduler);
    }
	
	 public void test() throws Exception {
	    	Factory factory = FactoryFactory.getFactory(FactoryFactory.FRACTAL_BACKEND);
	        Component root = (Component) factory.newComponent("helloworld.ClientServerImpl",new HashMap());
	        Fractal.getLifeCycleController(root).startFc();
	        ((java.lang.Runnable)root.getFcInterface("r")).run();
	        replaceScheduler(root);
	    }
	    
    public static void main(String[] args) throws Exception {      
    	HelloWorld h=new HelloWorld();
    	h.test();
    }
}

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