I have the following method in Java 8 and I'm working in project using java 7:
public <T> List<T> getValues(CommandLineItem commandLineItemMod, Class<T> targetClass) {
Object value = values.get(commandLineItemMod);
ArrayList<T> result = new ArrayList<>();
if (value instanceof Collection) {
Collection<?> sourceCollection = (Collection<?>) value;
result.ensureCapacity(sourceCollection.size());
sourceCollection.stream().map(o -> convertValue(o, targetClass)).forEach(result::add);
} else if (value != null) {
result.add(convertValue(value, targetClass));
}
return result;
}
my question is how I can transfer the following line from java 8 to java 7 :
sourceCollection.stream().map(o -> convertValue(o, targetClass)).forEach(result::add);
thank you for your help
The line
sourceCollection.stream().
.map(o -> convertValue(o, targetClass))
.forEach(result::add);
can be rewritten as:
for (Object o: sourceCollection) {
result.add(convertValue(o, targetClass));
}
which (IMO) is a clearer way to write the code in the first place.
Having said that, public (free) support for Java 7 ended in 2015, and premium (paid) support ended in Jul7 2019. (See https://www.oracle.com/java/technologies/java-se-support-roadmap.html). So the application you are working on is on borrowed time. I would have thought it would be more sensible to port the application to a newer Java version (or phase it out entirely) rather than expending valuable developer effort on backporting Java 8 code to it.
Java 7 doesn't support Stream API. You have to use a for loop:
for(Object source : sourceCollection){
result.add(convertValue(source, targetClass));
}
Related
I am migrating to .NET Core 3.X from .NETCore 2.2 and am trying to get following code to work
private static Task SetUserInformationReceived(UserInformationReceivedContext context)
{
if (context.User.TryGetValue(JwtClaimTypes.Role, value: out var roles)){
//Code comes here
}
}
But in .NET Core 3.X UserInformationReceivedContext.User is now a JsonDocument instead of JObject, rendering above code not usable. Is there any other way to get the JToken here with the specified property name?
I just found a solution for this question, and seeing there was no online solution, I'll be posting it here.
private static Task SetUserInformationReceived(UserInformationReceivedContext context){
if (context.User.RootElement.TryGetProperty(JwtClaimTypes.Role, value : out var roles)){
//Code comes here
}
}
Hope to find some guidance on this one soon, I've added reference for Windows IoT UWT in my project but still getting the following error ?
An exception of type 'System.TypeLoadException' occurred in test_led_alljoyn.exe but was not handled in user code
Additional information: Could not find Windows Runtime type 'Windows.Devices.Gpio.GpioController'.
Has anyone come across this issue while compiling applications for Raspberry Pi on Windows IoT core, on it's own one of my sample push button app works fine. Here's my code
public IAsyncOperation<testlightbulbSwitchResult> SwitchAsync(AllJoynMessageInfo info, bool interfaceMemberOn)
{
return (Task.Run(() =>
{
SwitchLED(interfaceMemberOn);
return testlightbulbSwitchResult.CreateSuccessResult();
}).AsAsyncOperation());
}
private void SwitchLED (bool state)
{
_ledState = state;
if (Windows.Foundation.Metadata.ApiInformation.IsTypePresent("Windows.Devices.Gpio.GpioController"))
{
this.tController = GpioController.GetDefault();
if (this.tController == null)
{
//GpioStatus.Text = "There is no GPIO controller on this device.";
//return;
this.tPin = this.tController.OpenPin(5);
this.tPin.Write(GpioPinValue.High);
this.tPin.SetDriveMode(GpioPinDriveMode.Output);
}
this.tPin.Write(_ledState ? GpioPinValue.Low : GpioPinValue.High);
}
}
Solved. I had to set build platform target compile with .net native tool chain.
// given a set of Item objects, group them by the managers of creator and owners
Map<String, List<Item>> managersItems =
itemSet.parallelStream().flatMap(item -> {
// get the list of the creator and owners
List<String> users = new ArrayList();
users.add(item.getCreator());
users.addAll(item.getOwners());
return Stream.of(users.toArray(new String[] {})).map(user -> {
LdapUserInfo ldapUser = LdapUserInfoFactory.create(user);
String manager = ldapUser.getManager();
return new AbstractMap.SimpleImmutableEntry<String, Item(manager, item);
});
}).collect(
Collectors.groupingBy(Map.Entry::getKey, Collectors.mapping(Map.Entry::getValue, Collectors.toList())));
This code compiles fine in Eclipse Mars, but gets the following eror in Eclipse Luna:
Type mismatch: cannot convert from Map<Object,List<Object>> to Map<String,List<WeblabInfo>>
If I do not assign the returned to a Map with Map<String, List<Item>> managersItem = in Eclipse Luna, the error is at Map.Entry::getKey and Map.Entry::getValue statement with message:
The type Map.Entry does not define getKey(Object) that is applicable here".
What did I do wrong?
You didn't do anything wrong. Eclipse compiler has problems with type inference that causes these issues. If Luna compatibility is important, you will have to add explicit types to lambda expressions. Try, for example, Map.Entry::<String,Item>getKey
On another note, it's not necessary to convert a List to array to stream it. You can directly call users.stream(). But even creating the List isn't necessary. You can use Stream.concat(Stream.of(item.getCreator()), item.getOwners().stream()) instead (granted, it's a bit unwieldy).
Finally (and most importantly), avoid using parallelStream with blocking code, such as looking up data in an external system. Parallel streams are designed to handle CPU-bound tasks.
I was able to come up with this solution from Misha's answer. This is working with Eclipse Luna Java compiler
Map<String, List<Item>> managersItems = itemSet
.stream()
.<Map.Entry<String, Item>> flatMap(item -> {
return Stream.concat(Stream.of(item.getCreatorLogin()), item.getOwners().stream()).map(
user -> {
LdapUserInfo ldapUser = LdapUserInfoFactory.create(user);
String manager = ldapUser.getManagerLoginName();
return new AbstractMap.SimpleEntry<String, Item>(manager, info);
});
})
.collect(Collectors.groupingBy(Map.Entry<String, Item>::getKey,
Collectors.mapping(Map.Entry<String, Item>::getValue,
Collectors.toList())));
Tech: Visual Studio 2010, Visual Studio Visualization & Modeling SDK
We have a commercial Visual Studio 2010 DSL, when we release a new version we want to increment the version number. I open the DslDefinition.dsl and update the version number as required and then do a Transform all templates so that the changes get reflected. The DslPackage 'source.extension.vsixmanifest' gets updated fine and shows the new version number.
The issue is however is that when someone opens a model created from version 1.0.0.0 with the updated version 1.0.0.1 then they can't open the model, the reason seems to be that the 'dslVersion' in the *.diagram file is set to 1.0.0.0 which has been outdated, I can fix by manually updating the dslVersion but there seems to be no way to set a supported version range.
Is there any fix for this?
I have solved this issue by overriding the 'CheckVersion' method which sits in the '*SerializationHelper' class. My implementation is below.
partial class ProductSerializationHelper
{
protected override void CheckVersion(Microsoft.VisualStudio.Modeling.SerializationContext serializationContext, System.Xml.XmlReader reader)
{
#region Check Parameters
global::System.Diagnostics.Debug.Assert(serializationContext != null);
if (serializationContext == null)
throw new global::System.ArgumentNullException("serializationContext");
global::System.Diagnostics.Debug.Assert(reader != null);
if (reader == null)
throw new global::System.ArgumentNullException("reader");
#endregion
global::System.Version expectedVersion = new global::System.Version("2.5.0.0");
string dslVersionStr = reader.GetAttribute("dslVersion");
if (dslVersionStr != null)
{
try
{
global::System.Version actualVersion = new global::System.Version(dslVersionStr);
// #### THIS IS WHERE I CHANGED FROM '!=' to '>'
if (actualVersion > expectedVersion)
{
ProductSerializationBehaviorSerializationMessages.VersionMismatch(serializationContext, reader, expectedVersion, actualVersion);
}
}
catch (global::System.ArgumentException)
{
ProductSerializationBehaviorSerializationMessages.InvalidPropertyValue(serializationContext, reader, "dslVersion", typeof(global::System.Version), dslVersionStr);
}
catch (global::System.FormatException)
{
ProductSerializationBehaviorSerializationMessages.InvalidPropertyValue(serializationContext, reader, "dslVersion", typeof(global::System.Version), dslVersionStr);
}
catch (global::System.OverflowException)
{
ProductSerializationBehaviorSerializationMessages.InvalidPropertyValue(serializationContext, reader, "dslVersion", typeof(global::System.Version), dslVersionStr);
}
}
}
}
What new features in java 7 is going to be implemented?
And what are they doing now?
Java SE 7 Features and Enhancements from JDK 7 Release Notes
This is the Java 7 new features summary from the OpenJDK 7 features page:
vm JSR 292: Support for dynamically-typed languages (InvokeDynamic)
Strict class-file checking
lang JSR 334: Small language enhancements (Project Coin)
core Upgrade class-loader architecture
Method to close a URLClassLoader
Concurrency and collections updates (jsr166y)
i18n Unicode 6.0
Locale enhancement
Separate user locale and user-interface locale
ionet JSR 203: More new I/O APIs for the Java platform (NIO.2)
NIO.2 filesystem provider for zip/jar archives
SCTP (Stream Control Transmission Protocol)
SDP (Sockets Direct Protocol)
Use the Windows Vista IPv6 stack
TLS 1.2
sec Elliptic-curve cryptography (ECC)
jdbc JDBC 4.1
client XRender pipeline for Java 2D
Create new platform APIs for 6u10 graphics features
Nimbus look-and-feel for Swing
Swing JLayer component
Gervill sound synthesizer [NEW]
web Update the XML stack
mgmt Enhanced MBeans [UPDATED]
Code examples for new features in Java 1.7
Try-with-resources statement
this:
BufferedReader br = new BufferedReader(new FileReader(path));
try {
return br.readLine();
} finally {
br.close();
}
becomes:
try (BufferedReader br = new BufferedReader(new FileReader(path)) {
return br.readLine();
}
You can declare more than one resource to close:
try (
InputStream in = new FileInputStream(src);
OutputStream out = new FileOutputStream(dest))
{
// code
}
Underscores in numeric literals
int one_million = 1_000_000;
Strings in switch
String s = ...
switch(s) {
case "quux":
processQuux(s);
// fall-through
case "foo":
case "bar":
processFooOrBar(s);
break;
case "baz":
processBaz(s);
// fall-through
default:
processDefault(s);
break;
}
Binary literals
int binary = 0b1001_1001;
Improved Type Inference for Generic Instance Creation
Map<String, List<String>> anagrams = new HashMap<String, List<String>>();
becomes:
Map<String, List<String>> anagrams = new HashMap<>();
Multiple exception catching
this:
} catch (FirstException ex) {
logger.error(ex);
throw ex;
} catch (SecondException ex) {
logger.error(ex);
throw ex;
}
becomes:
} catch (FirstException | SecondException ex) {
logger.error(ex);
throw ex;
}
SafeVarargs
this:
#SuppressWarnings({"unchecked", "varargs"})
public static void printAll(List<String>... lists){
for(List<String> list : lists){
System.out.println(list);
}
}
becomes:
#SafeVarargs
public static void printAll(List<String>... lists){
for(List<String> list : lists){
System.out.println(list);
}
}
New Feature of Java Standard Edition (JSE 7)
Decorate Components with the JLayer Class:
The JLayer class is a flexible and powerful decorator for Swing components. The JLayer class in Java SE 7 is similar in spirit to the JxLayer project project at java.net. The JLayer class was initially based on the JXLayer project, but its API evolved separately.
Strings in switch Statement:
In the JDK 7 , we can use a String object in the expression of a switch statement. The Java compiler generates generally more efficient bytecode from switch statements that use String objects than from chained if-then-else statements.
Type Inference for Generic Instance:
We can replace the type arguments required to invoke the constructor of a generic class with an empty set of type parameters (<>) as long as the compiler can infer the type arguments from the context. This pair of angle brackets is informally called the diamond.
Java SE 7 supports limited type inference for generic instance creation; you can only use type inference if the parameterized type of the constructor is obvious from the context. For example, the following example does not compile:
List<String> l = new ArrayList<>();
l.add("A");
l.addAll(new ArrayList<>());
In comparison, the following example compiles:
List<? extends String> list2 = new ArrayList<>();
l.addAll(list2);
Catching Multiple Exception Types and Rethrowing Exceptions with Improved Type Checking:
In Java SE 7 and later, a single catch block can handle more than one type of exception. This feature can reduce code duplication. Consider the following code, which contains duplicate code in each of the catch blocks:
catch (IOException e) {
logger.log(e);
throw e;
}
catch (SQLException e) {
logger.log(e);
throw e;
}
In releases prior to Java SE 7, it is difficult to create a common method to eliminate the duplicated code because the variable e has different types.
The following example, which is valid in Java SE 7 and later, eliminates the duplicated code:
catch (IOException|SQLException e) {
logger.log(e);
throw e;
}
The catch clause specifies the types of exceptions that the block can handle, and each exception type is separated with a vertical bar (|).
The java.nio.file package
The java.nio.file package and its related package, java.nio.file.attribute, provide comprehensive support for file I/O and for accessing the file system. A zip file system provider is also available in JDK 7.
Source: http://ohmjavaclasses.blogspot.com/
Java Programming Language Enhancements # Java7
Binary Literals
Strings in switch Statement
Try with Resources (How it works) or ARM (Automatic Resource Management)
Multiple Exception Handling
Suppressed Exceptions
underscore in literals
Type Inference for Generic Instance Creation using Diamond Syntax
Improved Compiler Warnings and Errors When Using Non-Reifiable Formal Parameters with Varargs Methods
Official reference
Official reference with java8
wiki reference
In addition to what John Skeet said, here's an overview of the Java 7 project. It includes a list and description of the features.
Note: JDK 7 was released on July 28, 2011, so you should now go to the official java SE site.
Language changes:
-Project Coin (small changes)
-switch on Strings
-try-with-resources
-diamond operator
Library changes:
-new abstracted file-system API (NIO.2) (with support for virtual filesystems)
-improved concurrency libraries
-elliptic curve encryption
-more incremental upgrades
Platform changes:
-support for dynamic languages
Below is the link explaining the newly added features of JAVA 7 , the explanation is crystal clear with the possible small examples for each features :
http://radar.oreilly.com/2011/09/java7-features.html
Using Diamond(<>) operator for generic instance creation
Map<String, List<Trade>> trades = new TreeMap <> ();
Using strings in switch statements
String status= “something”;
switch(statue){
case1:
case2:
default:
}
Underscore in numeric literals
int val 12_15;
long phoneNo = 01917_999_720L;
Using single catch statement for throwing multiple exception by using “|” operator
catch(IOException | NullPointerException ex){
ex.printStackTrace();
}
No need to close() resources because Java 7 provides try-with-resources statement
try(FileOutputStream fos = new FileOutputStream("movies.txt");
DataOutputStream dos = new DataOutputStream(fos)) {
dos.writeUTF("Java 7 Block Buster");
} catch(IOException e) {
// log the exception
}
binary literals with prefix “0b” or “0B”
I think ForkJoinPool and related enhancement to Executor Framework is an important addition in Java 7.
The following list contains links to the the enhancements pages in the Java SE 7.
Swing
IO and New IO
Networking
Security
Concurrency Utilities
Rich Internet Applications (RIA)/Deployment
Requesting and Customizing Applet Decoration in Dragg able Applets
Embedding JNLP File in Applet Tag
Deploying without Codebase
Handling Applet Initialization Status with Event Handlers
Java 2D
Java XML – JAXP, JAXB, and JAX-WS
Internationalization
java.lang Package
Multithreaded Custom Class Loaders in Java SE 7
Java Programming Language
Binary Literals
Strings in switch Statements
The try-with-resources Statement
Catching Multiple Exception Types and Rethrowing Exceptions with Improved Type Checking
Underscores in Numeric Literals
Type Inference for Generic Instance Creation
Improved Compiler Warnings and Errors When Using Non-Reifiable Formal Parameters with Varargs Methods
Java Virtual Machine (JVM)
Java Virtual Machine Support for Non-Java Languages
Garbage-First Collector
Java HotSpot Virtual Machine Performance Enhancements
JDBC
Reference 1 Reference 2