test/langtools/tools/javac/lambda/lambdaExpression/LambdaTest6.java

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/**
 * @test
 * @bug 8003280
 * @summary Add lambda tests
 *   Test bridge methods for certain SAM conversions
 *   Test the set of generated methods
 * @compile LambdaTest6.java
 * @run main LambdaTest6
 */

import java.lang.reflect.Method;
import java.util.HashSet;
import java.util.Set;

public class LambdaTest6<T> {

    interface H {Object m();}

    interface K<U> {void m(U element);}

    interface L extends K<String> {} //generic substitution

    interface M {void m(String s);}

    interface KM extends K<String>, M{} //generic substitution

    interface N extends H {String m();} //covariant return

    private static void assertTrue(boolean b) {
        if(!b)
            throw new AssertionError();
    }

    private Set<String> setOfStringObject() {
        Set<String> s = new HashSet<>();
        s.add("java.lang.String");
        s.add("java.lang.Object");
        return s;
    }

    private static Set<String> allowedMethods() {
        Set<String> s = new HashSet<>();
        s.add("m");
        return s;
    }

    private static boolean matchingMethodNames(Method[] methods) {
        Set<String> methodNames = new HashSet<>();
        for (Method m : methods) {
            methodNames.add(m.getName());
        }
        return methodNames.equals(allowedMethods());
    }

    private void test1()
    {
        L la = s -> { };
        la.m("hi");
        Class<? extends L> c1 = la.getClass();
        Method[] methods = c1.getDeclaredMethods();
        assertTrue(matchingMethodNames(methods));
        Set<String> types = setOfStringObject();
        for(Method m : methods) {
            if ("m".equals(m.getName())) {
                Class[] parameterTypes = m.getParameterTypes();
                assertTrue(parameterTypes.length == 1);
                assertTrue(types.remove(parameterTypes[0].getName()));
            }
        }
        assertTrue(types.isEmpty() || (types.size() == 1 && types.contains("java.lang.String")));
    }

    private void test2()
    {
        KM km = s -> { };
        //km.m("hi");
        Class<? extends KM> c2 = km.getClass();
        Method[] methods = c2.getDeclaredMethods();
        assertTrue(matchingMethodNames(methods));
        Set<String> types = setOfStringObject();
        for(Method m : methods) {
            if ("m".equals(m.getName())) {
                Class[] parameterTypes = m.getParameterTypes();
                assertTrue(parameterTypes.length == 1);
                assertTrue(types.remove(parameterTypes[0].getName()));
            }
        }
        assertTrue(types.isEmpty());
    }

    private void test3()
    {
        N na = ()-> "hi";
        assertTrue( na.m().equals("hi") );
        assertTrue( ((H)na).m().equals("hi") );
        Class<? extends N> c3 = na.getClass();
        Method[] methods = c3.getDeclaredMethods();
        assertTrue(matchingMethodNames(methods));
        Set<String> types = setOfStringObject();
        for(Method m : methods) {
            if ("m".equals(m.getName())) {
                Class returnType = m.getReturnType();
                assertTrue(types.remove(returnType.getName()));
            }
        }
        assertTrue(types.size() == 1); //there's a bridge
    }


    public static void main(String[] args) {
        LambdaTest6 test = new LambdaTest6();
        test.test1();
        test.test2();
        test.test3();
    }
}