What causes javac to issue the "uses unchecked or unsafe operations" warning

uses unchecked or unsafe operations. react native
some input files use unchecked or unsafe operations. flutter
java uses unchecked or unsafe operations vector
uses unchecked or unsafe operations. recompile with -xlint:unchecked for details. android
recompile with -xlint:unchecked for details
java uses unchecked or unsafe operations android studio
gradle xlint:unchecked
java test uses unchecked or unsafe operations

For example:

javac Foo.java
Note: Foo.java uses unchecked or unsafe operations.
Note: Recompile with -Xlint:unchecked for details.

This comes up in Java 5 and later if you're using collections without type specifiers (e.g., Arraylist() instead of ArrayList<String>()). It means that the compiler can't check that you're using the collection in a type-safe way, using generics.

To get rid of the warning, just be specific about what type of objects you're storing in the collection. So, instead of

List myList = new ArrayList();

use

List<String> myList = new ArrayList<String>();

In Java 7 you can shorten generic instantiation by using Type Inference.

List<String> myList = new ArrayList<>();

What causes javac to issue the “uses unchecked or , This develops up in Java 5 and later if you're doing collections without type specifiers (e.g., Arraylist() rather of ArrayList<String>()). It implies  What causes javac to issue the “uses unchecked or unsafe operations” warning

If you do what it suggests and recompile with the "-Xlint:unchecked" switch, it will give you more detailed information.

As well as the use of raw types (as described by the other answers), an unchecked cast can also cause the warning.

Once you've compiled with -Xlint, you should be able to rework your code to avoid the warning. This is not always possible, particularly if you are integrating with legacy code that cannot be changed. In this situation, you may decide to suppress the warning in places where you know that the code is correct:

@SuppressWarnings("unchecked")
public void myMethod()
{
    //...
}

[SOLVED] What causes javac to issue the "uses unchecked or , This comes up in Java 5 and later if you're using collections without type specifiers (e.g., Arraylist() instead of ArrayList<String>() ). It means that  The “unchecked or unsafe operations” warning was added when java added Generics, if I remember correctly. It’s usually asking you to be more explicit about types, in one way or another. For example. the code ArrayList foo = new ArrayList(); triggers that warning because javac is looking for ArrayList<String> foo = new ArrayList<String>();

For Android Studio, you need to add:

allprojects {

    gradle.projectsEvaluated {
        tasks.withType(JavaCompile) {
            options.compilerArgs << "-Xlint:unchecked"
        }
    }

    // ...
}

in your project's build.gradle file to know where this error is produced.

What causes javac to issue the “uses unchecked or , This comes up in Java 5 and later if you're using collections without type specifiers (e.g., Arraylist() instead of ArrayList<String>() ). It means that  What causes the Javac is not recognized error Step 1: Installing the Java Development Kit (JDK). Step 2: Setting the Java environment variable & updating the system path.

This warning means that your code operates on a raw type, recompile the example with the

-Xlint:unchecked 

to get the details

like this:

javac YourFile.java -Xlint:unchecked

Main.java:7: warning: [unchecked] unchecked cast
        clone.mylist = (ArrayList<String>)this.mylist.clone();
                                                           ^
  required: ArrayList<String>
  found:    Object
1 warning

docs.oracle.com talks about it here: http://docs.oracle.com/javase/tutorial/java/generics/rawTypes.html

java What causes javac to issue the "uses unchecked or unsafe , java What causes javac to issue the "uses unchecked or unsafe operations" warning? -Xlint:unchecked javac YourFile.java -Xlint:unchecked Main.java:7:  As well as the use of raw types (as described by the other answers), an unchecked cast can also cause the warning. Once you've compiled with -Xlint, you should be able to rework your code to avoid the warning.

for example when you call a function that returns Generic Collections and you don't specify the generic parameters yourself.

for a function

List<String> getNames()


List names = obj.getNames();

will generate this error.

To solve it you would just add the parameters

List<String> names = obj.getNames();

javac - Java programming language compiler, Then use the list file name on the javac command line, preceded by an @ character. In this case, the compiler will issue a warning if any such class files are It also makes it unnecessary to specify a separate destination directory with -d. Resolving The Problem. Increase the size of /tmp filesystem or manager the data in /tmp so the javac has some space available to it to compile files.

Lesson: Common Problems (and Their Solutions) (The Java , This beginner Java tutorial describes getting started with Java and setting up Here's an error caused by omitting a semicolon ( ; ) at the end of a statement:. The javac tool reads class and interface definitions, written in the Java programming language, and compiles them into bytecode class files. It can also process annotations in Java source files and classes. There are two ways to pass source code file names to javac: For a small number of source files, simply list the file names on the command line.

Javac not recognized as internal or external command, How to resolve the error 'Javac not recognized as internal or external command' and how to set JDK path. When compiling a java program from command line, the most common issue For some reason, I find user PATH not to be working. Mixing lambda expressions and inner classes, similar to the following example, can cause the javac tool to crash.

'javac' is not recognized as an internal or external command, It means that javac.exe executable file, which exists in bin directory of JDK Even I was having the same issue and I did following 2 things which finally worked for a broken called brakets that had a path file so I deleted it, probably makes no  However, if the extension is enabled or negotiated, the server certificate changing restriction is not necessary and will be discarded accordingly. In case of compatibility issues, an application may disable negotiation of this extension by setting the System Property jdk.tls.useExtendedMasterSecret to false in the JDK.

Comments
  • In Java 7, I got the same warning even using Type Interference with this collection: ConcurrentHashMap<Integer, Object> objs = new ConcurrentHashMap()
  • @Lucio You still need angle brackets. new ConcurrentHashMap<>()
  • Just to point out, this is not collections specific. You get the error because Java compiler can't ensure type safety in general. For example, same warning is produced with the following code: AbstractMap.SimpleEntry<String, String> entry = new AbstractMap.SimpleEntry("hello", "world");
  • -Xlint:unchecked with MAVEN
  • I wish more people would upvote this answer. I stand by my selection of @Bill the Lizard's answer, but this answer is close to my heart for showing me that the answer was staring me right in the face in the warning itself as well as elaborating another reason for encountering the error.
  • This is the ultimate answer!
  • I think it does. He links to the Oracle documentation for this exact warning.