-Akey[=value]

Options to pass to annotation processors. These are not interpreted by javac directly, but are made available for use by individual processors. key should be one or more identifiers separated by ".".

-cp path or -classpath path

Specify where to find user class files, and (optionally) annotation processors and source files. This class path overrides the user class path in the CLASSPATH environment variable. If neither CLASSPATH, -cp nor -classpath is specified, the user class path consists of the current directory. See Setting the Class Path for more details.
>If the -sourcepath option is not specified, the user class path is also searched for source files.
If the -processorpath option is not specified, the class path is also searched for annotation processors.

-Djava.ext.dirs=directories

Override the location of installed extensions.

-Djava.endorsed.dirs=directories

Override the location of endorsed standards path.

-d directory

Set the destination directory for class files. The directory must already exist; javac will not create it. If a class is part of a package, javac puts the class file in a subdirectory reflecting the package name, creating directories as needed. For example, if you specify -d /home/myclasses and the class is called com.mypackage.MyClass, then the class file is called /home/myclasses/com/mypackage/MyClass.class.
If -d is not specified, javac puts each class files in the same directory as the source file from which it was generated.
Note: The directory specified by -d is not automatically added to your user class path.

-deprecation

Show a description of each use or override of a deprecated member or class. Without -deprecation, javac shows a summary of the source files that use or override deprecated members or classes. -deprecation is shorthand for -Xlint:deprecation.

-encoding encoding

Set the source file encoding name, such as EUC-JP and UTF-8. If -encoding is not specified, the platform default converter is used.

-endorseddirs directories

Override the location of endorsed standards path.

-extdirs directories

Overrides the location of the ext directory. The directories variable is a colon-separated list of directories. Each JAR archive in the specified directories is searched for class files. All JAR archives found are automatically part of the class path.
If you are cross-compiling (compiling classes against bootstrap and extension classes of a different Java platform implementation), this option specifies the directories that contain the extension classes. See Cross-Compilation Options for more information.

-g

Generate all debugging information, including local variables. By default, only line number and source file information is generated.

-g:none

Do not generate any debugging information.

-g:{keyword list}

Generate only some kinds of debugging information, specified by a comma separated list of keywords. Valid keywords are:

-help

Print a synopsis of standard options.

-implicit:{class,none}

Controls the generation of class files for implicitly loaded source files. To automatically generate class files, use -implicit:class. To suppress class file generation, use -implicit:none. If this option is not specified, the default is to automatically generate class files. In this case, the compiler will issue a warning if any such class files are generated when also doing annotation processing. The warning will not be issued if this option is set explicitly. See Searching For Types.

-Joption

Pass option to the java launcher called by javac. For example, -J-Xms48m sets the startup memory to 48 megabytes. It is a common convention for -J to pass options to the underlying VM executing applications written in Java.
Note: CLASSPATH, -classpath, -bootclasspath, and -extdirs do not specify the classes used to run javac. Fiddling with the implementation of the compiler in this way is usually pointless and always risky. If you do need to do this, use the -J option to pass through options to the underlying java launcher.

-nowarn

Disable warning messages. This has the same meaning as -Xlint:none.

-proc: {none,only}

Controls whether annotation processing and/or compilation is done. -proc:none means that compilation takes place without annotation processing. -proc:only means that only annotation processing is done, without any subsequent compilation.

-processor class1[,class2,class3...]

Names of the annotation processors to run. This bypasses the default discovery process.

-processorpath path

Specify where to find annotation processors; if this option is not used, the class path will be searched for processors.

-s dir

Specify the directory where to place generated source files. The directory must already exist; javac will not create it. If a class is part of a package, the compiler puts the source file in a subdirectory reflecting the package name, creating directories as needed. For example, if you specify -s /home/mysrc and the class is called com.mypackage.MyClass, then the source file will be placed in /home/mysrc/com/mypackage/MyClass.java.

-source release

Specifies the version of source code accepted. The following values for release are allowed:

-sourcepath sourcepath

Specify the source code path to search for class or interface definitions. As with the user class path, source path entries are separated by colons (:) and can be directories, JAR archives, or ZIP archives. If packages are used, the local path name within the directory or archive must reflect the package name.
Note: Classes found through the class path may be subject to automatic recompilation if their sources are also found. See Searching For Types.

-verbose

Verbose output. This includes information about each class loaded and each source file compiled.

-version

Print version information.

-Werror

Terminate compilation if warnings occur.

-X

Display information about non-standard options and exit.

-target version

Generate class files that target a specified version of the VM. Class files will run on the specified target and on later versions, but not on earlier versions of the VM. Valid targets are 1.1, 1.2, 1.3, 1.4, 1.5 (also 5), 1.6 (also 6), and 1.7 (also 7).

The default for -target depends on the value of -source:

-bootclasspath bootclasspath

Cross-compile against the specified set of boot classes. As with the user class path, boot class path entries are separated by colons (:) and can be directories, JAR archives, or ZIP archives.

-Xbootclasspath/p:path

Prepend to the bootstrap class path.

-Xbootclasspath/a:path

Append to the bootstrap class path.

-Xbootclasspath/:path

Override location of bootstrap class files.

-Xlint

Enable all recommended warnings. In this release, enabling all available warnings is recommended.

-Xlint:all

Enable all recommended warnings. In this release, enabling all available warnings is recommended.

-Xlint:none

Disable all warnings.

-Xlint:name

Enable warning name. See the section Warnings That Can Be Enabled or Disabled with -Xlint Option for a list of warnings you can enable with this option.

-Xlint:-name

Disable warning name. See the section Warnings That Can Be Enabled or Disabled with -Xlint Option for a list of warnings you can disable with this option.

-Xmaxerrs number

Set the maximum number of errors to print.

-Xmaxwarns number

Set the maximum number of warnings to print.

-Xstdout filename

Send compiler messages to the named file. By default, compiler messages go to System.err.

-Xprefer:{newer,source}

Specify which file to read when both a source file and class file are found for a type. (See Searching For Types). If -Xprefer:newer is used, it reads the newer of the source or class file for a type (default). If the -Xprefer:source option is used, it reads source file. Use -Xprefer:source when you want to be sure that any annotation processors can access annotations declared with a retention policy of SOURCE.

-Xpkginfo:{always,legacy,nonempty}

Specify handling of package-info files

-Xprint

Print out textual representation of specified types for debugging purposes; perform neither annotation processing nor compilation. The format of the output may change.

-XprintProcessorInfo

Print information about which annotations a processor is asked to process.

-XprintRounds

Print information about initial and subsequent annotation processing rounds.

cast

Warn about unnecessary and redundant casts. For example:

String s = (String)"Hello!"

classfile

Warn about issues related to classfile contents.

deprecation

Warn about use of deprecated items. For example:

    java.util.Date myDate = new java.util.Date();


    int currentDay = myDate.getDay();

The method java.util.Date.getDay has been deprecated since JDK 1.1.

dep-ann

Warn about items that are documented with an @deprecated Javadoc comment, but do not have a @Deprecated annotation. For example:

  /**


   * @deprecated As of Java SE 7, replaced by {@link #newMethod()}


   */


  public static void deprecatedMethood() { }


  public static void newMethod() { }

divzero

Warn about division by constant integer 0. For example:

    int divideByZero = 42 / 0;

empty

Warn about empty statements after if statements. For example:

class E {


    void m() {


        if (true) ;


    }
}

fallthrough

Check switch blocks for fall-through cases and provide a warning message for any that are found. Fall-through cases are cases in a switch block, other than the last case in the block, whose code does not include a break statement, allowing code execution to "fall through" from that case to the next case. For example, the code following the case 1 label in this switch block does not end with a break statement:

switch (x) {
case 1:


       System.out.println("1");


       //  No break statement here.
case 2:


       System.out.println("2");
}

If the -Xlint:fallthrough flag were used when compiling this code, the compiler would emit a warning about "possible fall-through into case," along with the line number of the case in question.

finally

Warn about finally clauses that cannot complete normally. For example:

  public static int m() {


    try {


      throw new NullPointerException();


    } catch (NullPointerException e) {


      System.err.println("Caught NullPointerException.");


      return 1;


    } finally {


      return 0;


    }


  }

The compiler generates a warning for finally block in this example. When this method is called, it returns a value of 0, not 1. A finally block always executes when the try block exits. In this example, if control is transferred to the catch, then the method exits. However, the finally block must be executed, so it is executed, even though control has already been transferred outside the method.

options

Warn about issues relating to the use of command line options. See Cross-Compilation Example for an example of this kind of warning.

overrides

Warn about issues regarding method overrides. For example, consider the following two classes:

public class ClassWithVarargsMethod {


  void varargsMethod(String... s) { }
}

public class ClassWithOverridingMethod extends ClassWithVarargsMethod {


  @Override


  void varargsMethod(String[] s) { }
}

The compiler generates a warning similar to the following:
warning: [override] varargsMethod(String[]) in ClassWithOverridingMethod overrides varargsMethod(String...) in ClassWithVarargsMethod; overriding method is missing '...'
When the compiler encounters a varargs method, it translates the varargs formal parameter into an array. In the method ClassWithVarargsMethod.varargsMethod, the compiler translates the varargs formal parameter String... s to the formal parameter String[] s, an array, which matches the formal parameter of the method ClassWithOverridingMethod.varargsMethod. Consequently, this example compiles.

path

Warn about invalid path elements and nonexistent path directories on the command line (with regards to the class path, the source path, and other paths). Such warnings cannot be suppressed with the @SuppressWarnings annotation. For example:

javac -Xlint:path -classpath /nonexistentpath Example.java

processing

Warn about issues regarding annotation processing. The compiler generates this warning if you have a class that has an annotation, and you use an annotation processor that cannot handle that type of exception. For example, the following is a simple annotation processor:
Source file AnnoProc.java:

import java.util.*;
import javax.annotation.processing.*;
import javax.lang.model.*;
import javax.lang.model.element.*;
@SupportedAnnotationTypes("NotAnno")
public class AnnoProc extends AbstractProcessor {


    public boolean process(Set<? extends TypeElement> elems, RoundEnvironment renv) {


        return true;


    }


    public SourceVersion getSupportedSourceVersion() {


        return SourceVersion.latest();


    }
}

Source file AnnosWithoutProcessors.java:

@interface Anno { }
@Anno
class AnnosWithoutProcessors { }

The following commands compile the annotation processor AnnoProc, then run this annotation processor against the source file AnnosWithoutProcessors.java:

% javac AnnoProc.java
% javac -cp . -Xlint:processing -processor AnnoProc -proc:only AnnosWithoutProcessors.java

When the compiler runs the annotation processor against the source file AnnosWithoutProcessors.java, it generates the following warning:
warning: [processing] No processor claimed any of these annotations: Anno
To resolve this issue, you can rename the annotation defined and used in the class AnnosWithoutProcessors from Anno to NotAnno.

rawtypes

Warn about unchecked operations on raw types. The following statement generates a rawtypes warning:

void countElements(List l) { ... }

The following does not generate a rawtypes warning:

void countElements(List<?> l) { ... }

List is a raw type. However, List<?> is a unbounded wildcard parameterized type. Because List is a parameterized interface, you should always specify its type argument. In this example, the List formal argument is specified with a unbounded wildcard (?) as its formal type parameter, which means that the countElements method can accept any instantiation of the List interface.

serial

Warn about missing serialVersionUID definitions on serializable classes. For example:

public class PersistentTime implements Serializable
{


  private Date time;


   public PersistentTime() {


     time = Calendar.getInstance().getTime();


   }


   public Date getTime() {


     return time;


   }
}

The compiler generates the following warning:
warning: [serial] serializable class PersistentTime has no definition of serialVersionUID
If a serializable class does not explicitly declare a field named serialVersionUID, then the serialization runtime will calculate a default serialVersionUID value for that class based on various aspects of the class, as described in the Java Object Serialization Specification. However, it is strongly recommended that all serializable classes explicitly declare serialVersionUID values because the default process of computing serialVersionUID vales is highly sensitive to class details that may vary depending on compiler implementations, and can thus result in unexpected InvalidClassExceptions during deserialization. Therefore, to guarantee a consistent serialVersionUID value across different Java compiler implementations, a serializable class must declare an explicit serialVersionUID value.

static

Warn about issues relating to use of statics. For example:

class XLintStatic {


    static void m1() { }


    void m2() { this.m1(); }
}

The compiler generates the following warning:

warning: [static] static method should be qualified by type name, XLintStatic, instead of by an expression

To resolve this issue, you can call the static method m1 as follows:

XLintStatic.m1();

Alternatively, you can remove the static keyword from the declaration of the method m1.

try

Warn about issues relating to use of try blocks, including try-with-resources statements. For example, a warning is generated for the following statement because the resource ac declared in the try statement is not used:

try ( AutoCloseable ac = getResource() ) {


    // do nothing
}

unchecked

Give more detail for unchecked conversion warnings that are mandated by the Java Language Specification. For example:

    List l = new ArrayList<Number>();


    List<String> ls = l;       // unchecked warning

During type erasure, the types ArrayList<Number> and List<String> become ArrayList and List, respectively.
The variable ls has the parameterized type List<String>. When the List referenced by l is assigned to ls, the compiler generates an unchecked warning; the compiler is unable to determine at compile time, and moreover knows that the JVM will not be able to determine at runtime, if l refers to a List<String> type; it does not. Consequently, heap pollution occurs.
In detail, a heap pollution situation occurs when the List object l, whose static type is List<Number>, is assigned to another List object, ls, that has a different static type, List<String>. However, the compiler still allows this assignment. It must allow this assignment to preserve backwards compatibility with versions of Java SE that do not support generics. Because of type erasure, List<Number> and List<String> both become List. Consequently, the compiler allows the assignment of the object l, which has a raw type of List, to the object ls.

varargs

Warn about unsafe usages of variable arguments (varargs) methods, in particular, those that contain non-reifiable arguments. For example:

public class ArrayBuilder {


  public static <T> void addToList (List<T> listArg, T... elements) {


    for (T x : elements) {


      listArg.add(x);


    }


  }
}

The compiler generates the following warning for the definition of the method ArrayBuilder.addToList:

warning: [varargs] Possible heap pollution from parameterized vararg type T

When the compiler encounters a varargs method, it translates the varargs formal parameter into an array. However, the Java programming language does not permit the creation of arrays of parameterized types. In the method ArrayBuilder.addToList, the compiler translates the varargs formal parameter T... elements to the formal parameter T[] elements, an array. However, because of type erasure, the compiler converts the varargs formal parameter to Object[] elements. Consequently, there is a possibility of heap pollution.