Develop Reference

VS code & java: This setting is deprecated, please use 'java.jdt.ls.java.home' instead

I faced this error when I was trying to set up Java in my vs code. In my settings.json:
"java.home": "C:\\Program Files\\Java\\jdk-17.0.22"
but the error says This setting is deprecated, please use 'java.jdt.ls.java.home' instead.
What is wrong here?

What is wrong here?
You are using a setting name that has been deprecated. This setting is still probably still going to work ... for now ... but it is likely that it will stop working completely in a future release.
So what you need to do is to change your "settings.xml" to use "java.jdt.ls.java.home" as the property name instead of "java.home". It would be advisable to do this as soon as practical.
Note that there is more information on the VSCode for Java settings here. The current version of the page says this:
java.home : Deprecated, please use 'java.jdt.ls.java.home' instead. Absolute path to JDK home folder used to launch the Java Language Server. Requires VS Code restart.
However, if your real problem is that VSCode is telling you that your version of the Java JDK is incompatible and you need to download a new one, first read https://stackoverflow.com/questions/71042056/. Downloading a new JDK (as suggested by VSCode) may not be the best solution.

assert keyword(cannot resolve symbol assert)

GridBlock firstBlock =grid.getEntranceBlock(); //enter through entrance
assert(firstBlock!=null);
The above assert keyword is flaged by the IDEA and I don't understand why. If i try to compile i get an warning "Warning:(83, 25) java: as of release 1.4, 'assert' is a keyword, and may not be used as an identifier
(use -source 1.4 or higher to use 'assert' as a keyword)". As I understand you can use assert without having to import anything. Now i don't understand what I am missing. I tried download new JDK but it didn't help. I m using Intellij

Check what "language level" your project is using: File > Project Structure > Project > Project language level
You might be on a very old level for some reason. If there's no reason to be on it, just try increasing it to something more modern -- this will also give you other very useful language features.

package com.sun.xml.internal.messaging.saaj.soap.dynamic does not exist

I am trying to compile a java file, which uses package com.sun.xml.internal.messaging.saaj.soap.dynamic, using ANT-1.9.3 but I'm receiving error
package com.sun.xml.internal.messaging.saaj.soap.dynamic does not
exist
I tried compiling both JDK7 and JDK 8 and getting the same error.
I can see the package exist inside rt.jar of both JDK. I have set JAVA_HOME also properly.
Can someone help me to resolve this issue?

Unfortunately for you, this behaviour is probably intentional and your usage is deliberately unsupported. If your code used to compile under Java6 and now doesn't under Java7 or Java8 then you've basically fallen foul of
From one release to another, these classes may be removed, or they may be moved from one package to another
http://www.oracle.com/technetwork/java/faq-sun-packages-142232.html
See also http://bugs.java.com/bugdatabase/view_bug.do?bug_id=6778491 for a technical description of a possible cause of not being able to compile a class which references a 'com.sun.*' class but which throws the same compiler error you're seeing despite the fact that the referenced class exists in rt.jar. Also for the kind of response which Oracle give to bug reports relating to it;)
Unfortunately, using undocumented, unsupported APIs often has this kind of 'bite you in the posterior' kind of effect.

Please add the line, < compilerarg line="-XDignore.symbol.file" compiler="modern"/ > for < javac > tag in your build.xml. This should solve your problem. It solved for me.
For reference you can view the forum link
http://www.icesoft.org/JForum/posts/list/19871.page#sthash.srrN9Ijk.dpbs

Java backward compatibility doesn't work

I've created library for encoding/decoding property files. Library has two main purposes:
Encode property file and save it to another file.
Return key value from encoded file (decode file, store result as string in memory, load string to Properties object and return result from properties object).
Everything seems to work fine but today I've noticed that library doesn't work on java 1.5. I've noticed that problem occurs on decoding side so let's focus on this code. Assume that code responsible for decoding looks like that:
String props = "key1=val1\nkey2=val2";
Properties p = new Properties();
p.load(new StringReader(props));
p.list(System.out);
After few tests I saw that the problem is with this line:
p.load(new StringReader(props));
I found that Properties class in java 1.5 doesn't have load(Reader) declaration. To meet java 1.5 API requirements I changed this line to load(InputStream). Everyting works fine now but here is the question.
I use gradle to compile project and I knew that this library should work on java 1.5+ ( I've java 1.7 installed on my computer) so I added to build.gradle those two lines
sourceCompatibility = '1.5'
targetCompatibility = '1.5'
I thought that java compiler will know that I want to compile code with compatibility to java 1.5 and will show appropriate errors. To be sure that it isn't gradle problem I compiled java code from command line but with the same result (compiler doesn't show any errors). So why compiler doesn't show any errors while compiling?
Java 1.5 Properties class API: http://docs.oracle.com/javase/1.5.0/docs/api/java/util/Properties.html
Java 1.6 Properties class API: http://docs.oracle.com/javase/6/docs/api/java/util/Properties.html
[UPDATE]
Neither -source or -target will check API compatibility. If so how can I check it in gradle? As millimoose wrote maven has this plugin (http://mojo.codehaus.org/animal-sniffer-maven-plugin/index.html) but what with gradle?

See the sections of the javac documents named "cross-compiling" and "Cross-Compilation Example".
http://docs.oracle.com/javase/7/docs/technotes/tools/solaris/javac.html#crosscomp-options
Specifically this part:
It is important to use -bootclasspath and -extdirs when
cross-compiling; see Cross-Compilation Example below ....... If you do not
specify the correct version of bootstrap classes, the compiler will
use the old language rules (in this example, it will use version 1.6
of the Java programming language) combined with the new bootstrap
classes, which can result in class files that do not work on the older
platform (in this case, Java SE 6) because reference to non-existent
methods can get included.

The -source switch only instructs the compiler to give a compilation error if you use a language construct not supported in the specified version. For example using try-with-resources with -source 1.6 will result in a compilation error, as it is only supported in Java 7 and higher. Its use is more a sanity check (ie: is my code still compatible with Java version 1.x)
The -target switch instructs the compiler to emit byte code compatible with the specified version. That is: the compiled code can run on the virtual machines of the specified version.
However neither of these switches make the compiler check for compatibility with Java libraries of an earlier Java version. That is why since Java 7, the compiler gives a warning if you use -target 1.6 (or earlier), that you should also specify the -bootclasspath to point to a Java runtime library set of that java version so that it can check if your code is only using classes and methods of that Java version.

How to compile java project with false #Override in eclipse/java/android?

I have dowloades the sources of the android musicplayer vanilla. When i compile it with eclipse i get several compiler-error
that complain that a method with #Override is not an override.
I made the source compilable by removing the false #Overrides.
I donot know, why there are these wrong #Overrides.
Maybe they are there because the autor developed for an other android-baseclasslibrary that has these methods while my
java 6 with android 2.1 does not have it.
Is there a way to make it compileable without deleting the false #Overrides?

You need to switch to JDK6 :
Enable Java 1.6 Compiler in your project properties under Java Compiler
Make sure your java Runtime Environement is at 1.6

The problem may come from using different versions.
It's not a good practice to make it compileable without deleting the false #Overrides because it is made for a reason and if you CAN disable it, you may have problems elsewhere and you wouldn't know where the problems are happening
So, just delete the false or check for a newer version of vanilla