StackOverflow2013

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copied!<p>If you are using <strong>Android Studio</strong>, the Java 7 <em>language</em> should be enabled automatically without any patches. Try-with-resource requires API Level 19+, and NIO 2.0 stuff are missing. </p> <p>If you can't use Java 7 features, see <a href="https://stackoverflow.com/a/17309063/224671">@Nuno</a>'s answer on how to edit your <code>build.gradle</code>.</p> <p>The following is for historical interest only.</p> <hr> <p>A small part of Java 7 can certainly be used with Android (note: I have only tested on 4.1). </p> <p>First of all, you could not use Eclipse's ADT because <a href="https://android.googlesource.com/platform/sdk/+/master/eclipse/plugins/com.android.ide.eclipse.adt/src/com/android/ide/eclipse/adt/AdtConstants.java" rel="nofollow noreferrer">it is hard-coded</a> that only Java compiler 1.5 and 1.6 are compliant. You could recompile ADT but I find there is no simple way to do that aside from recompiling the whole Android together. </p> <p>But you don't need to use Eclipse. For instance, <a href="http://tools.android.com/recent/androidstudio032released" rel="nofollow noreferrer"><strong>Android Studio 0.3.2</strong></a>, <a href="http://www.jetbrains.com/idea/" rel="nofollow noreferrer"><strong>IntelliJ IDEA CE</strong></a> and other javac-based IDEs supports compiling to Android <i>and</i> you could set the compliance even up to Java 8 with:</p> <ul> <li>File → Project Structure → Modules → (pick the module at the 2nd pane) → Language level → (choose "7.0 - Diamonds, ARM, multi-catch, etc.")</li> </ul> <p><img src="https://i.stack.imgur.com/1z7iH.png" alt="Enabling Java 7 on IntelliJ"></p> <p>This only allows Java 7 <strong>language features</strong>, and you can hardly benefit from anything since a half of improvement also comes from the library. Features you could use are those which do not depend on the library:</p> <ul> <li>Diamond operator (<code><></code>)</li> <li>String switch</li> <li>Multiple-catch (<code>catch (Exc1 | Exc2 e)</code>)</li> <li>Underscore in number literals (<code>1_234_567</code>)</li> <li>Binary literals (<code>0b1110111</code>)</li> </ul> <p>And these features cannot be used <em>yet</em>:</p> <ul> <li>The <code>try</code>-with-resources statement — because it requires the non-existing interface "java.lang.AutoCloseable" (this can be used publicly in 4.4+)</li> <li>The @SafeVarargs annotation — because "java.lang.SafeVarargs" does not exist</li> </ul> <p>... "yet" :) It turns out that, although Android's library is targeting for 1.6, the Android source does contain interfaces like <a href="https://android.googlesource.com/platform/libcore/+/master/luni/src/main/java/java/lang/AutoCloseable.java" rel="nofollow noreferrer">AutoCloseable</a> and traditional interfaces like <a href="https://android.googlesource.com/platform/libcore/+/master/luni/src/main/java/java/io/Closeable.java" rel="nofollow noreferrer">Closeable</a> does inherit from AutoCloseable (SafeVarargs is really missing, though). We could confirm its existence via reflection. They are hidden simply because the Javadoc has the <code>@hide</code> tag, which caused the "android.jar" not to include them.</p> <p>There is already as existing question<strong> <a href="https://stackoverflow.com/questions/7888191/how-do-i-build-the-android-sdk-with-hidden-and-internal-apis-available">How do I build the Android SDK with hidden and internal APIs available?</a> </strong>on how to get those methods back. You just need to <em>replace</em> the existing "android.jar" reference of the current Platform with our customized one, then many of the Java 7 APIs will become available (the procedure is similar to that in Eclipse. Check Project Structure → SDKs.)</p> <p>In additional to AutoCloseable, (only) the following Java 7 <strong>library features</strong> are also revealed:</p> <ul> <li>Exception chaining constructors in ConcurrentModificationException, LinkageError and AssertionError</li> <li>The static .compare() methods for primitives: Boolean.compare(), Byte.compare(), Short.compare(), Character.compare(), Integer.compare(), Long.compare().</li> <li><a href="http://docs.oracle.com/javase/7/docs/api/java/util/Currency.html" rel="nofollow noreferrer">Currency</a>: .getAvailableCurrencies(), .getDisplayName() (but <em>without</em> .getNumericCode())</li> <li><a href="http://docs.oracle.com/javase/7/docs/api/java/util/BitSet.html" rel="nofollow noreferrer">BitSet</a>: .previousSetBit(), .previousClearBit(), .valueOf(), .toLongArray(), .toByteArray()</li> <li><a href="http://docs.oracle.com/javase/7/docs/api/java/util/Collections.html" rel="nofollow noreferrer">Collections</a>: .emptyEnumeration(), .emptyIterator(), .emptyListIterator()</li> <li><a href="http://docs.oracle.com/javase/7/docs/api/java/lang/AutoCloseable.html" rel="nofollow noreferrer">AutoCloseable</a></li> <li><a href="http://docs.oracle.com/javase/7/docs/api/java/lang/Throwable.html" rel="nofollow noreferrer">Throwable</a>: .addSuppressed(), .getSuppressed(), and the 4-argument constructor</li> <li><a href="http://docs.oracle.com/javase/7/docs/api/java/lang/Character.html" rel="nofollow noreferrer">Character</a>: .compare(), .isSurrogate(), .getName(), .highSurrogate(), .lowSurrogate(), .isBmpCodePoint() (but <em>without</em> .isAlphabetic() and .isIdeographic())</li> <li>System: .lineSeparator() (undocumented?)</li> <li><a href="http://docs.oracle.com/javase/7/docs/api/java/lang/reflect/Modifier.html" rel="nofollow noreferrer">java.lang.reflect.Modifier</a>: .classModifiers(), .constructorModifiers(), .fieldModifiers(), .interfaceModifiers(), .methodModifiers()</li> <li><a href="http://docs.oracle.com/javase/7/docs/api/java/net/NetworkInterface.html" rel="nofollow noreferrer">NetworkInterface</a>: .getIndex(), .getByIndex()</li> <li><a href="http://docs.oracle.com/javase/7/docs/api/java/net/InetSocketAddress.html" rel="nofollow noreferrer">InetSocketAddress</a>: .getHostString()</li> <li><a href="http://docs.oracle.com/javase/7/docs/api/java/net/InetAddress.html" rel="nofollow noreferrer">InetAddress</a>: .getLoopbackAddress()</li> <li><a href="http://docs.oracle.com/javase/7/docs/api/java/util/logging/Logger.html" rel="nofollow noreferrer">Logger</a>: .getGlobal()</li> <li><a href="http://docs.oracle.com/javase/7/docs/api/java/util/concurrent/ConcurrentLinkedDeque.html" rel="nofollow noreferrer">ConcurrentLinkedDeque</a></li> <li><a href="http://docs.oracle.com/javase/7/docs/api/java/util/concurrent/locks/AbstractQueuedSynchronizer.html" rel="nofollow noreferrer">AbstractQueuedSynchronizer</a>: .hasQueuedPredecessors()</li> <li><a href="http://docs.oracle.com/javase/7/docs/api/java/util/zip/DeflaterOutputStream.html" rel="nofollow noreferrer">DeflaterOutputStream</a>: the 3 constructors with "syncFlush".</li> <li><a href="http://docs.oracle.com/javase/7/docs/api/java/util/zip/Deflater.html" rel="nofollow noreferrer">Deflater</a>: .NO_FLUSH, .SYNC_FLUSH, .FULL_FLUSH, .deflate() with 4 arguments</li> </ul> <p>That's basically all. In particular, NIO 2.0 does not exist, and Arrays.asList is still not @SafeVarargs.</p>

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