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.WrongMethodTypeException
While 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.AsynchronousChannelProvider
NIO.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.FileTypeDetector
The 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.TransferQueue
The 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.HttpHandler
The 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].
As Java developer I used to monitor the new features of Java very closely. As Code Cop my focus on programming languages is much broader. Currently I am working with clients using C#, Java, JavaScript, Kotlin, Oracle PL/SQL, PHP, Python and TypeScript. (And I would love a few more clients using some F#, Go or 
