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Groovy example source code file (GenericsTest.groovy)

This example Groovy source code file (GenericsTest.groovy) is included in the DevDaily.com "Java Source Code Warehouse" project. The intent of this project is to help you "Learn Java by Example" TM.

Java - Groovy tags/keywords

a, a, arraylist, arraylist, b, b, callabletask, cloneable, list, list, ljava/util/collection, map, string, t

The Groovy GenericsTest.groovy source code

/*
 * Copyright 2003-2010 the original author or authors.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
package gls.generics

import org.codehaus.groovy.control.MultipleCompilationErrorsException

class GenericsTest extends GenericsTestBase {

    public void testClassWithoutParameterExtendsClassWithFixedParameter() {
        createClassInfo """
            class B extends ArrayList<Long> {}
        """
        assert signatures == [
                "class": "Ljava/util/ArrayList<Ljava/lang/Long;>;Lgroovy/lang/GroovyObject;",
        ]
    }

    public void testMultipleImplementsWithParameter() {
        createClassInfo """
            abstract class B<T> implements Runnable,List {}
        """
        assert signatures == ["class": "<T:Ljava/lang/Object;>Ljava/lang/Object;Ljava/lang/Runnable;Ljava/util/List;Lgroovy/lang/GroovyObject;"]
    }

    public void testImplementsWithParameter() {
        createClassInfo """
            abstract class B<T> implements List {}
        """
        assert signatures == ["class": "<T:Ljava/lang/Object;>Ljava/lang/Object;Ljava/util/List;Lgroovy/lang/GroovyObject;"]
    }

    public void testExtendsWithParameter() {
        createClassInfo """
            class B<T> extends ArrayList {}
        """
        assert signatures == ["class": "<T:Ljava/lang/Object;>Ljava/util/ArrayList;Lgroovy/lang/GroovyObject;"]
    }

    public void testNestedExtendsWithParameter() {
        createClassInfo """
            class B<T> extends HashMap> {}
        """
        assert signatures == ["class": "<T:Ljava/lang/Object;>Ljava/util/HashMap;>;Lgroovy/lang/GroovyObject;"]
    }

    public void testBoundInterface() {
        createClassInfo """
            class B<T extends List> {}
        """
        assert signatures == ["class": "<T::Ljava/util/List;>Ljava/lang/Object;Lgroovy/lang/GroovyObject;"]
    }

    public void testNestedReuseOfParameter() {
        createClassInfo """
            class B<Y,T extends Map> {}
        """
        assert signatures == ["class": "<Y:Ljava/lang/Object;T::Ljava/util/Map;>Ljava/lang/Object;Lgroovy/lang/GroovyObject;"]
    }

    public void testFieldWithParameter() {
        createClassInfo """
            class B { public Collection<Integer> books }
        """
        assert signatures == [books: "Ljava/util/Collection<Ljava/lang/Integer;>;"]
    }

    public void testFieldReusedParameter() {
        createClassInfo """
            class B<T> { public Collection collection }
        """
        assert signatures == ["class": "<T:Ljava/lang/Object;>Ljava/lang/Object;Lgroovy/lang/GroovyObject;",
                collection: "Ljava/util/Collection<TT;>;"]
    }

    public void testParameterAsReturnType() {
        createClassInfo """
            class B {
                static <T> T foo() {return null}
            }
        """
        assert signatures == ["foo()Ljava/lang/Object;": "<T:Ljava/lang/Object;>()TT;"]
    }

    public void testParameterAsReturnTypeAndParameter() {
        createClassInfo """
            class B {
                static <T> T foo(T t) {return null}
            }
        """
        assert signatures == ["foo(Ljava/lang/Object;)Ljava/lang/Object;": "<T:Ljava/lang/Object;>(TT;)TT;"]
    }

    public void testParameterAsMethodParameter() {
        createClassInfo """
            class B<T> {
                void foo(T t){}
            }
        """
        assert signatures == ["class": "<T:Ljava/lang/Object;>Ljava/lang/Object;Lgroovy/lang/GroovyObject;",
                "foo(Ljava/lang/Object;)V": "(TT;)V"]
    }

    public void testParameterAsNestedMethodParameter() {
        createClassInfo """
            class B<T> {
                void foo(List<T> t){}
            }
        """
        assert signatures == ["class": "<T:Ljava/lang/Object;>Ljava/lang/Object;Lgroovy/lang/GroovyObject;",
                "foo(Ljava/util/List;)V": "(Ljava/util/List<TT;>;)V"]
    }

    public void testParameterAsNestedMethodParameterReturningInterface() {
        createClassInfo """
            class B<T> {
                Cloneable foo(List<T> t){}
            }
        """
        assert signatures == ["class": "<T:Ljava/lang/Object;>Ljava/lang/Object;Lgroovy/lang/GroovyObject;",
                "foo(Ljava/util/List;)Ljava/lang/Cloneable;": "(Ljava/util/List<TT;>;)Ljava/lang/Cloneable;"]
    }

    public void testArray() {
        createClassInfo """
            class B<T> {
                T[] get(T[] arr) {return null}
            }
        """
        assert signatures == ["class": "<T:Ljava/lang/Object;>Ljava/lang/Object;Lgroovy/lang/GroovyObject;",
                "get([Ljava/lang/Object;)[Ljava/lang/Object;": "([TT;)[TT;"]
    }

    public void testMultipleBounds() {
        createClassInfo """
            class Pair<    A extends Comparable 
            {
                A foo(){}
                B bar(){}
            }
        """
        assert signatures ==
                ["class": "<A::Ljava/lang/Comparable;>Ljava/lang/Object;Lgroovy/lang/GroovyObject;",
                        "foo()Ljava/lang/Comparable;": "()TA;",
                        "bar()Ljava/lang/Cloneable;": "()TB;"]
    }

    public void testWildCard() {
        createClassInfo """
            class B {
                private Collection<?> f1 
                private List<? extends Number> f2 
                private Comparator<? super String> f3 
                private Map<String,?> f4  
            }
        """
        assert signatures == [
                f1: "Ljava/util/Collection<*>;",
                f2: "Ljava/util/List<+Ljava/lang/Number;>;",
                f3: "Ljava/util/Comparator<-Ljava/lang/String;>;",
                f4: "Ljava/util/Map<Ljava/lang/String;*>;"
        ]
    }

    public void testParameterAsParameterForReturnTypeAndFieldClass() {
        createClassInfo """
               public class B<T> {
                   private T owner;
                   public Class<T> getOwnerClass(){}
   
            } 
        """
        assert signatures == [
                "class": "<T:Ljava/lang/Object;>Ljava/lang/Object;Lgroovy/lang/GroovyObject;",
                "owner": "TT;",
                "getOwnerClass()Ljava/lang/Class;": "()Ljava/lang/Class<TT;>;"
        ]
    }

    public void testInterfaceWithParameter() {
        createClassInfo """
            interface B<T> {}
        """
        assert signatures == ["class": "<T:Ljava/lang/Object;>Ljava/lang/Object;"]
    }


    public void testTypeParamAsBound() {
        createClassInfo """
    class Box<A> {
      public <V extends A> void foo(V v) {
      }

    }
        """
        assert signatures == ["foo(Ljava/lang/Object;)V": "<V:TA;>(TV;)V", "class": "Ljava/lang/Object;Lgroovy/lang/GroovyObject;"]
    }

    public void testInvalidParameterUsage() {
        shouldNotCompile """
            abstract class B<T> implements Map{}
        """
        shouldNotCompile """
            class A<T,V> extends ArrayList{}
        """
        shouldNotCompile """
            class A<T extends Number> {}
            class B<T> extends A{}
        """
        shouldNotCompile """
            class B<T> extends ArrayList{}
        """
    }

    void testCovariantReturn() {
        shouldNotCompile """
          class A<T> {
              T foo(T t) {1}
           }

          class B extends A<Long>{
              String foo(Long l){"2"}
          }
        """

        assertScript """
          class A<T> {
              T foo(T t) {1}
           }

          class B extends A<Long>{
              Long foo(Long l){2}
          }
          def b = new B();
          try {
            b.foo(new Object())
            assert false
          } catch (ClassCastException cce) {
            assert true
          }
          assert b.foo((Long) 1) == 2
        """
    }

    void testCovariantReturnWithInterface() {
        assertScript """
        import java.util.concurrent.*

        class CallableTask implements Callable<String> {
          public String call() { "x" }
        } 
        
        def task = new CallableTask()
        assert task.call() == "x"
      """
    }

    void testCovariantReturnWithEmptyAbstractClassesInBetween() {
        assertScript """
        import java.util.concurrent.*;

        abstract class AbstractCallableTask<T> implements Callable { }
        abstract class SubclassCallableTask<T> extends AbstractCallableTask { }
        class CallableTask extends SubclassCallableTask<String> {
          public String call() { return "x"; }
        }
        assert "x" == new CallableTask().call();
      """
    }

    void testGenericsDiamondShortcutSimple() {
        assertScript """
            List<List list1 = new ArrayList<>()
            assert list1.size() == 0
        """
    }

    void testGenericsDiamondShortcutComplex() {
        assertScript """
            List<List>>> list2 = new ArrayList<>()
            assert list2.size() == 0
        """
    }

    void testGenericsDiamondShortcutMethodCall() {
        assertScript """
            def method(List<List list3) {
              list3.size()
            }

            assert method(new ArrayList<>()) == 0
        """
    }

    void testGenericsDiamondShortcutIllegalPosition() {
        assertScriptAndVerifyCompilationError """
            List<> list4 = []
        """, 'unexpected token: <'
    }

    void testGenericsInAsType() {
        // this is to ensure no regression to GROOVY-2725 will happen
        // "as ThreadLocal<Integer>\n" did not compile because the nls
        // was swallowed and could not be used to end the expression
        assertScript """
import java.util.concurrent.atomic.AtomicInteger

 public class ThreadId
 {
  private static final AtomicInteger nextId = new AtomicInteger(0)
  private static final ThreadLocal<Integer> threadId = [
                  initialValue: { return nextId.getAndIncrement() }
                  ] as ThreadLocal<Integer>

  public static int get()
  {
      System.out.println( "Thread ID: " + threadId.get());
      return threadId.get();
  }

 }
 // we do not actually want to execute something, just
 // ensure this compiles, so we do a dummy command here
 assert ThreadId!=null
       """
    }

    void testCompilationWithMissingClosingBracketsInGenerics() {
        assertScriptAndVerifyCompilationError """
            def list1 = new ArrayList<Integer()
        """

        assertScriptAndVerifyCompilationError """
            List<Integer list2 = new ArrayList {}
        """

        assertScriptAndVerifyCompilationError """
            abstract class ArrayList2<E> extends AbstractList {}
        """

        assertScriptAndVerifyCompilationError """
            abstract class ArrayList3<E> extends AbstractList implements List>()
        """

        assertScriptAndVerifyCompilationError """
            def List<List history = new ArrayList()
        """
    }

    private void assertScriptAndVerifyCompilationError(scriptText) {
        assertScriptAndVerifyCompilationError(scriptText, "Missing closing bracket '>' for generics types")
    }

    private void assertScriptAndVerifyCompilationError(scriptText, errorMessage) {
        try {
            assertScript scriptText
            fail("The script compilation should have failed as it contains mis-matching generic brackets")
        } catch (MultipleCompilationErrorsException mcee) {
            def text = mcee.toString();
            assert text.contains(errorMessage)
        }
    }

    void testGenericsInfoForClosureParameters() {
        def cl = { List<String> s -> }
        def type = cl.getClass().getMethod("call", List).genericParameterTypes[0]
        assert type.toString().contains("java.util.List<java.lang.String>")

        type = cl.getClass().getMethod("doCall", List).genericParameterTypes[0]
        assert type.toString().contains("java.util.List<java.lang.String>")
    }
}

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