Tue, 14 May 2013 11:11:09 -0700
8012556: Implement lambda methods on interfaces as static
8006140: Javac NPE compiling Lambda expression on initialization expression of static field in interface
Summary: Lambdas occurring in static contexts or those not needing instance information should be generated into static methods. This has long been the case for classes. However, as a work-around to the lack of support for statics on interfaces, interface lambda methods have been generated into default methods. For lambdas in interface static contexts (fields and static methods) this causes an NPE in javac because there is no 'this'. MethodHandles now support static methods on interfaces. This changeset allows lambda methods to be generated as static interface methods. An existing bug in Hotspot (8013875) is exposed in a test when the "-esa" flag is used. This test and another test that already exposed this bug have been marked with @ignore.
Reviewed-by: mcimadamore
1 /*
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3 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
4 *
5 * This code is free software; you can redistribute it and/or modify it
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7 * published by the Free Software Foundation.
8 *
9 * This code is distributed in the hope that it will be useful, but WITHOUT
10 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
11 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
12 * version 2 for more details (a copy is included in the LICENSE file that
13 * accompanied this code).
14 *
15 * You should have received a copy of the GNU General Public License version
16 * 2 along with this work; if not, write to the Free Software Foundation,
17 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
18 *
19 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
20 * or visit www.oracle.com if you need additional information or have any
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22 */
24 /**
25 * @test
26 * @bug 8003280
27 * @summary Add lambda tests
28 * This test is for lambda expressions
29 * @compile LambdaTest1.java
30 * @run main LambdaTest1
31 */
33 import java.util.Collections;
34 import java.util.List;
35 import java.util.ArrayList;
37 public class LambdaTest1 {
38 public static void main(String[] args) {
40 LambdaTest1 test = new LambdaTest1();
42 test.method2((int n) -> { });
43 test.method2((int n) -> { });
44 test.method2((int n) -> { return; }); // ";" is mandatory here
45 test.method2((int n) -> { System.out.println(n); }); // ";" is optional here
46 test.method2(n -> { System.out.println(n); }); //warning, explict type required for n?
48 test.method3(()-> { System.out.println("implementing VoidVoid.vvMethod()"); });
49 test.method3(() -> {});
51 test.method4(()-> 42);
52 test.method4(()-> { return 42; });//";" is mandatory here
54 test.method5((int n)-> n+1);
55 test.method5((int n) -> 42);
56 test.method5((int n) -> { return 42; });
57 test.method5(
58 (int n) -> { //"{" optional here
59 if(n > 0)
60 return n++;
61 else
62 return n--;
63 }
64 );
66 Runnable r = ()-> { System.out.println("Runnable.run() method implemented"); };
67 r.run();
68 ((Runnable)()-> { System.out.println("Runnable.run() method implemented"); }).run();
69 }
71 void method2(VoidInt a) {
72 System.out.println("method2()");
73 final int N = 1;
74 int n = 2; //effectively final variable
75 System.out.println("method2() \"this\":" + this);
76 ((Runnable)
77 ()->{
78 System.out.println("inside lambda \"this\":" + this);
79 System.out.println("inside lambda accessing final variable N:" + N);
80 System.out.println("inside lambda accessing effectively final variable n:" + n);
81 }
82 ).run();
83 //n++; //compile error if n is modified
84 a.viMethod(2);
85 }
87 void method3(VoidVoid a) {
88 System.out.println("method3()");
89 a.vvMethod();
90 }
92 void method4(IntVoid a) {
93 System.out.println("method4()");
94 System.out.println(a.ivMethod());
95 }
97 void method5(IntInt a) {
98 System.out.println("method5()");
99 System.out.println(a.iiMethod(5));
100 }
103 //SAM type interfaces
104 interface VoidInt {
105 void viMethod(int n);
106 }
108 interface VoidVoid {
109 void vvMethod();
110 }
112 interface IntVoid {
113 int ivMethod();
114 }
116 interface IntInt {
117 int iiMethod(int n);
118 }
119 }