Blame openjdk/nashorn/samples/LambdaAsFunc.java

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/*
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 * Copyright (c) 2015, Oracle and/or its affiliates. All rights reserved.
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 * are met:
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 *
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 */
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import javax.script.*;
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import java.util.function.*;
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// example demonstrating that arbitrary Lambda can be called as function from script
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public class LambdaAsFunc {
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    public static void main(String[] args) throws Exception {
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        ScriptEngineManager m = new ScriptEngineManager();
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        ScriptEngine e = m.getEngineByName("nashorn");
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        // expose a lambda as top-level script function
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        e.put("upper", (Function<String, String>) String::toUpperCase);
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        // call lambda as though it is a normal script function
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        System.out.println(e.eval("upper('hello')"));
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    }
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}