bind,cmd/gomobile: add a new generator for Java API wrappers

Using the new Java class analyzer API, scan the bound packages
for references to Java classes and interfaces and generate Go
wrappers for them.

This is the second part of the implementation of proposal golang/go#16876.

For golang/go#16876

Change-Id: I59ec0ebdae0081a615dc34d450f344c20c03f871
Reviewed-on: https://go-review.googlesource.com/28596
Reviewed-by: David Crawshaw <crawshaw@golang.org>

bind/java/ClassesTest.java

@@ -0,0 +1,68 @@
+// Copyright 2016 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package go;
+
+import android.test.InstrumentationTestCase;
+import android.test.MoreAsserts;
+
+import java.io.InputStream;
+import java.io.IOException;
+import java.util.Arrays;
+import java.util.Random;
+
+import go.javapkg.Javapkg;
+
+public class ClassesTest extends InstrumentationTestCase {
+	public void testConst() {
+		assertEquals("const Float", Float.MIN_VALUE, Javapkg.floatMin());
+		assertEquals("const String", java.util.jar.JarFile.MANIFEST_NAME, Javapkg.manifestName());
+		assertEquals("const Int", 7, Integer.SIZE, Javapkg.integerBytes());
+	}
+
+	public void testFunction() {
+		Javapkg.systemCurrentTimeMillis();
+	}
+
+	public void testMethod() {
+		try {
+			assertEquals("Integer.decode", 0xff, Javapkg.integerDecode("0xff"));
+		} catch (Exception e) {
+			throw new RuntimeException(e);
+		}
+		Exception exc = null;
+		try {
+			Javapkg.integerDecode("obviously wrong");
+		} catch (Exception e) {
+			exc = e;
+		}
+		assertNotNull("IntegerDecode Exception", exc);
+	}
+
+	public void testOverloadedMethod() {
+		try {
+			assertEquals("Integer.parseInt", 0xc4, Javapkg.integerParseInt("c4", 16));
+		} catch (Exception e) {
+			throw new RuntimeException(e);
+		}
+		Exception exc = null;
+		try {
+			Javapkg.integerParseInt("wrong", 16);
+		} catch (Exception e) {
+			exc = e;
+		}
+		assertNotNull("integerParseInt Exception", exc);
+		assertEquals("Integer.valueOf", 42, Javapkg.integerValueOf(42));
+	}
+
+	public void testException() {
+		Exception exc = null;
+		try {
+			Javapkg.provokeRuntimeException();
+		} catch (Exception e) {
+			exc = e;
+		}
+		assertNotNull("RuntimeException", exc);
+	}
+}