Four years after the last major release, Java 7 was released July 28th 2011. It brought several new features, the most commonly mentioned were the Diamond Operator, using strings in switch statements, automatic resource management, numeric literals with underscores and improved exception handling. Further there were additions to NIO, the Fork/Join framework and invokedynamic. You have probably heard of all these things by now. There were also some minor additions, but the previous ones have been talked about since long before Java 7 was released.A good start to check the new features of Java 7 is the presentation about the 55 New Features You (Probably) Didn't Hear About. It also covers some lesser known additions. For a complete list of all changes see the Java 7 Release Notes. They are really worth reading, and include links into the Java Tutorial for more complex topics.
Classlist
Always when a new version of Java comes out, I take a look at its new classes, using my Java Class File Parser. The list of new classes complements the list of new features. Java 7 adds 211 public classes to
rt.jar, where Java 6 had 490 and Java 5 even added 547. So it looks like a smaller release.invokedynamic
I heard that a lot of work went into the
invokedynamic byte code instruction which was added to the JVM. It comes with a small, new package java.lang.invoke.java.lang.invoke.CallSite java.lang.invoke.ConstantCallSite java.lang.invoke.MethodHandle java.lang.invoke.MethodHandleProxies java.lang.invoke.MethodHandles java.lang.invoke.MethodType java.lang.invoke.MutableCallSite java.lang.invoke.SwitchPoint java.lang.invoke.VolatileCallSite java.lang.invoke.WrongMethodTypeExceptionWhile this package contains just ten classes, there are another 16 package access classes (not shown here), so
invokedynamic is definitely more complex than it looks.NIO Channels
A more practical addition are some new NIO channels, most noteworthy the
AsynchronousChannels, which allow network and file access in an asynchronous way, together with their exceptions.java.nio.channels.AcceptPendingException java.nio.channels.AlreadyBoundException java.nio.channels.AsynchronousByteChannel java.nio.channels.AsynchronousChannel java.nio.channels.AsynchronousChannelGroup java.nio.channels.AsynchronousFileChannel java.nio.channels.AsynchronousServerSocketChannel java.nio.channels.AsynchronousSocketChannel java.nio.channels.CompletionHandler java.nio.channels.IllegalChannelGroupException java.nio.channels.InterruptedByTimeoutException java.nio.channels.MembershipKey java.nio.channels.MulticastChannel java.nio.channels.NetworkChannel java.nio.channels.ReadPendingException java.nio.channels.SeekableByteChannel java.nio.channels.ShutdownChannelGroupException java.nio.channels.WritePendingException java.nio.channels.spi.AsynchronousChannelProviderNIO.2
The new
java.nio.file package is the largest addition, it contains a brand new API for file access together with file attributes like POSIX permissions, file system and file storage abstractions.java.nio.file.AccessDeniedException java.nio.file.AccessMode java.nio.file.AtomicMoveNotSupportedException java.nio.file.ClosedDirectoryStreamException java.nio.file.ClosedFileSystemException java.nio.file.ClosedWatchServiceException java.nio.file.CopyOption java.nio.file.DirectoryIteratorException java.nio.file.DirectoryNotEmptyException java.nio.file.DirectoryStream java.nio.file.FileAlreadyExistsException java.nio.file.Files java.nio.file.FileStore java.nio.file.FileSystem java.nio.file.FileSystemAlreadyExistsException java.nio.file.FileSystemException java.nio.file.FileSystemLoopException java.nio.file.FileSystemNotFoundException java.nio.file.FileSystems java.nio.file.FileVisitOption java.nio.file.FileVisitor java.nio.file.FileVisitResult java.nio.file.InvalidPathException java.nio.file.LinkOption java.nio.file.LinkPermission java.nio.file.NoSuchFileException java.nio.file.NotDirectoryException java.nio.file.NotLinkException java.nio.file.OpenOption java.nio.file.Path java.nio.file.PathMatcher java.nio.file.Paths java.nio.file.ProviderMismatchException java.nio.file.ProviderNotFoundException java.nio.file.ReadOnlyFileSystemException java.nio.file.SecureDirectoryStream java.nio.file.SimpleFileVisitor java.nio.file.StandardCopyOption java.nio.file.StandardOpenOption java.nio.file.StandardWatchEventKinds java.nio.file.Watchable java.nio.file.WatchEvent java.nio.file.WatchKey java.nio.file.WatchService java.nio.file.attribute.AclEntry java.nio.file.attribute.AclEntryFlag java.nio.file.attribute.AclEntryPermission java.nio.file.attribute.AclEntryType java.nio.file.attribute.AclFileAttributeView java.nio.file.attribute.AttributeView java.nio.file.attribute.BasicFileAttributes java.nio.file.attribute.BasicFileAttributeView java.nio.file.attribute.DosFileAttributes java.nio.file.attribute.DosFileAttributeView java.nio.file.attribute.FileAttribute java.nio.file.attribute.FileAttributeView java.nio.file.attribute.FileOwnerAttributeView java.nio.file.attribute.FileStoreAttributeView java.nio.file.attribute.FileTime java.nio.file.attribute.GroupPrincipal java.nio.file.attribute.PosixFileAttributes java.nio.file.attribute.PosixFileAttributeView java.nio.file.attribute.PosixFilePermission java.nio.file.attribute.PosixFilePermissions java.nio.file.attribute.UserDefinedFileAttributeView java.nio.file.attribute.UserPrincipal java.nio.file.attribute.UserPrincipalLookupService java.nio.file.attribute.UserPrincipalNotFoundException java.nio.file.spi.FileSystemProvider java.nio.file.spi.FileTypeDetectorThe new abstraction for files is the
Path, and the helper classes Files and Paths are the main entry points for using the new functionality. The good old java.io.File is not deprecated but considered legacy from now on. Now plain Java can do everything and we do not need to include commons-io any more.JSR 166y Concurrency Additions
JSR 166y added the Fork/Join framework and a few concurrency related classes which did not make it into Java 5 on time, where the original JSR 166 went in.
java.util.concurrent.ConcurrentLinkedDeque java.util.concurrent.ForkJoinPool java.util.concurrent.ForkJoinTask java.util.concurrent.ForkJoinWorkerThread java.util.concurrent.LinkedTransferQueue java.util.concurrent.Phaser java.util.concurrent.RecursiveAction java.util.concurrent.RecursiveTask java.util.concurrent.ThreadLocalRandom java.util.concurrent.TransferQueueThe main class is the
ForkJoinPool together with its two workers, RecursiveAction and RecursiveTask.Other Classes
There are several new classes all over the JDK,
java.awt.SecondaryLoop java.beans.Transient java.lang.AutoCloseable java.lang.BootstrapMethodError java.lang.ClassValue java.lang.ReflectiveOperationException java.lang.SafeVarargs java.lang.management.BufferPoolMXBean java.lang.management.PlatformLoggingMXBean java.lang.management.PlatformManagedObject java.net.ProtocolFamily java.net.SocketOption java.net.StandardProtocolFamily java.net.StandardSocketOptions java.nio.charset.StandardCharsets java.security.AlgorithmConstraints java.security.CryptoPrimitive java.security.cert.CertificateRevokedException java.security.cert.CRLReason java.security.cert.Extension java.security.cert.PKIXReason java.sql.PseudoColumnUsage java.util.IllformedLocaleException java.util.Objects javax.crypto.AEADBadTagException javax.crypto.spec.GCMParameterSpec javax.net.ssl.ExtendedSSLSession javax.net.ssl.X509ExtendedTrustManager javax.print.attribute.standard.DialogTypeSelection javax.security.auth.kerberos.KeyTab javax.sound.midi.MidiDeviceReceiver javax.sound.midi.MidiDeviceTransmitter javax.sql.rowset.RowSetFactory javax.sql.rowset.RowSetProvider javax.swing.border.StrokeBorder javax.swing.JLayer javax.swing.Painter javax.swing.plaf.nimbus.AbstractRegionPainter javax.swing.plaf.nimbus.NimbusLookAndFeel javax.swing.plaf.nimbus.NimbusStyle javax.swing.plaf.nimbus.State javax.xml.bind.JAXBPermission javax.xml.ws.EndpointContext javax.xml.ws.spi.Invoker javax.xml.ws.spi.http.HttpContext javax.xml.ws.spi.http.HttpExchange javax.xml.ws.spi.http.HttpHandlerThe changes cover additions to UI capabilities, e.g.
NimbusLookAndFeel, new security algorithms and updated JDBC, XML and WS packages. The most interesting classes are AutoCloseable for the new try-with-resources statement and Objects with its requireNonNull(T obj) method.Summary
Java 7 has some nice additions to core Java, but still feels like a smaller release, not as ground breaking as Java 5. The most useful thing might be the Diamond Operator because it saves a lot of typing.
See the complete list of all classes available in Java 7. Each class name is annotated with [release] showing the release it first appeared, e.g.
java.lang.annotation.Annotation [5]. Package access classes are indicated by a lowercase p, e.g. java.lang.CharacterName [7p].
