https://openjdk.java.net/ 
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package com.sun.jdi;

import java.util.List;


A point within the executing code of the target VM.
Locations are used to identify the current position of
a suspended thread (analogous to an instruction pointer or
program counter register in native programs). They are also used
to identify the position at which to set a breakpoint.


The availability of a line number for a location will
depend on the level of debugging information available from the
target VM.

 Several mirror interfaces have locations. Each such mirror extends a Locatable interface. 

Strata


The source information for a Location is dependent on the
stratum which is used. A stratum is a source code
level within a sequence of translations.  For example,
say the baz program is written in the programming language
"Foo" then translated to the language "Bar" and finally
translated into the Java programming language.  The
Java programming language stratum is named
"Java", let's say the other strata are named "Foo" and "Bar". A given location (as viewed by the sourceName() and lineNumber() methods) might be at line 14 of "baz.foo" in the "Foo"
stratum, line 23 of "baz.bar" in the "Bar"
stratum and line 71 of the "Java" stratum. Note that while the Java programming language may have only one source file for a reference type, this restriction does not apply to other strata - thus each Location should be consulted to determine its source path. Queries which do not specify a stratum (sourceName(), sourcePath() and lineNumber()) use the VM's default stratum (VirtualMachine.getDefaultStratum()). If the specified stratum (whether explicitly specified by a method parameter or implicitly as the VM's default) is null or is not available in the declaring type, the declaring type's default stratum is used (declaringType().
defaultStratum()). Note that in the normal case, of code that originates as Java programming language source, there will be only one stratum ("Java") and it will be returned as the default. To determine the available strata use ReferenceType.availableStrata(). 
Author:Robert Field, Gordon Hirsch, James McIlree
See Also:
Since:1.3
/**
 * A point within the executing code of the target VM.
 * Locations are used to identify the current position of
 * a suspended thread (analogous to an instruction pointer or
 * program counter register in native programs). They are also used
 * to identify the position at which to set a breakpoint.
 * <p>
 * The availability of a line number for a location will
 * depend on the level of debugging information available from the
 * target VM.
 * <p>
 * Several mirror interfaces have locations. Each such mirror
 * extends a {@link Locatable} interface.
 * <p>
 * <a name="strata"><b>Strata</b></a>
 * <p>
 * The source information for a Location is dependent on the
 * <i>stratum</i> which is used. A stratum is a source code
 * level within a sequence of translations.  For example,
 * say the baz program is written in the programming language
 * "Foo" then translated to the language "Bar" and finally
 * translated into the Java programming language.  The
 * Java programming language stratum is named
 * <code>"Java"</code>, let's say the other strata are named
 * "Foo" and "Bar".  A given location (as viewed by the
 * {@link #sourceName()} and {@link #lineNumber()} methods)
 * might be at line 14 of "baz.foo" in the <code>"Foo"</code>
 * stratum, line 23 of "baz.bar" in the <code>"Bar"</code>
 * stratum and line 71 of the <code>"Java"</code> stratum.
 * Note that while the Java programming language may have
 * only one source file for a reference type, this restriction
 * does not apply to other strata - thus each Location should
 * be consulted to determine its source path.
 * Queries which do not specify a stratum
 * ({@link #sourceName()}, {@link #sourcePath()} and
 * {@link #lineNumber()}) use the VM's default stratum
 * ({@link VirtualMachine#getDefaultStratum()}).
 * If the specified stratum (whether explicitly specified
 * by a method parameter or implicitly as the VM's default)
 * is <code>null</code> or is not available in the declaring
 * type, the declaring type's default stratum is used
 * ({@link #declaringType()}.{@link ReferenceType#defaultStratum()
 * defaultStratum()}).  Note that in the normal case, of code
 * that originates as Java programming language source, there
 * will be only one stratum (<code>"Java"</code>) and it will be
 * returned as the default.  To determine the available strata
 * use {@link ReferenceType#availableStrata()}.
 *
 * @see com.sun.jdi.request.EventRequestManager
 * @see StackFrame
 * @see com.sun.jdi.event.BreakpointEvent
 * @see com.sun.jdi.event.ExceptionEvent
 * @see Locatable
 *
 * @author Robert Field
 * @author Gordon Hirsch
 * @author James McIlree
 * @since 1.3
 */
@jdk.Exported
public interface Location extends Mirror, Comparable<Location> {

    
Gets the type to which this Location belongs. Normally the declaring type is a ClassType, but executable locations also may exist within the static initializer of an InterfaceType. 
Returns:the ReferenceType containing this Location.
/**
     * Gets the type to which this Location belongs. Normally
     * the declaring type is a {@link ClassType}, but executable
     * locations also may exist within the static initializer of an
     * {@link InterfaceType}.
     *
     * @return the {@link ReferenceType} containing this Location.
     */
    ReferenceType declaringType();

    
Gets the method containing this Location.

Returns:the location's Method.
/**
     * Gets the method containing this Location.
     *
     * @return the location's {@link Method}.
     */
    Method method();

    
Gets the code position within this location's method.

Returns:the long representing the position within the method
or -1 if location is within a native method.
/**
     * Gets the code position within this location's method.
     *
     * @return the long representing the position within the method
     * or -1 if location is within a native method.
     */
    long codeIndex();

    
Gets an identifing name for the source corresponding to
this location.


This method is equivalent to
sourceName(vm.getDefaultStratum()) - see sourceName(String) for more information. 
Throws:
Returns:a string specifying the source
/**
     * Gets an identifing name for the source corresponding to
     * this location.
     * <P>
     * This method is equivalent to
     * <code>sourceName(vm.getDefaultStratum())</code> -
     * see {@link #sourceName(String)}
     * for more information.
     *
     * @return a string specifying the source
     * @throws AbsentInformationException if the source name is not
     * known
     */
    String sourceName() throws AbsentInformationException;


    
Gets an identifing name for the source corresponding to
this location. Interpretation of this string is the
responsibility of the source repository mechanism.


Returned name is for the specified stratum (see the class comment for a description of strata). 

The returned string is the unqualified name of the source
file for this Location.  For example,
java.lang.Thread would return
"Thread.java".

Params:
  • stratum – The stratum to retrieve information from
or null for the declaring type's
default stratum.
Throws:
Returns:a string specifying the source
Since:1.4
/**
     * Gets an identifing name for the source corresponding to
     * this location. Interpretation of this string is the
     * responsibility of the source repository mechanism.
     * <P>
     * Returned name is for the specified <i>stratum</i>
     * (see the {@link Location class comment} for a
     * description of strata).
     * <P>
     * The returned string is the unqualified name of the source
     * file for this Location.  For example,
     * <CODE>java.lang.Thread</CODE> would return
     * <CODE>"Thread.java"</CODE>.
     *
     * @param stratum The stratum to retrieve information from
     * or <code>null</code> for the declaring type's
     * default stratum.
     *
     * @return a string specifying the source
     *
     * @throws AbsentInformationException if the source name is not
     * known
     *
     * @since 1.4
     */
    String sourceName(String stratum)
                        throws AbsentInformationException;

    
Gets the path to the source corresponding to this
location.


This method is equivalent to
sourcePath(vm.getDefaultStratum()) - see sourcePath(String) for more information. 
Throws:
Returns:a string specifying the source
/**
     * Gets the path to the source corresponding to this
     * location.
     * <P>
     * This method is equivalent to
     * <code>sourcePath(vm.getDefaultStratum())</code> -
     * see {@link #sourcePath(String)}
     * for more information.
     *
     * @return a string specifying the source
     *
     * @throws AbsentInformationException if the source name is not
     * known
     */
    String sourcePath() throws AbsentInformationException;


    
Gets the path to the source corresponding to this
location. Interpretation of this string is the
responsibility of the source repository mechanism.


Returned path is for the specified stratum (see the class comment for a description of strata). 
 In the reference implementation, for strata which do not explicitly specify source path (the Java programming language stratum never does), the returned string is the package name of declaringType() converted to a platform dependent path followed by the unqualified name of the source file for this Location (sourceName(stratum)). For example, on a Windows platform, java.lang.Thread
would return
"java\lang\Thread.java".

Params:
  • stratum – The stratum to retrieve information from
or null for the declaring type's
default stratum.
Throws:
Returns:a string specifying the source
Since:1.4
/**
     * Gets the path to the source corresponding to this
     * location. Interpretation of this string is the
     * responsibility of the source repository mechanism.
     * <P>
     * Returned path is for the specified <i>stratum</i>
     * (see the {@link Location class comment} for a
     * description of strata).
     * <P>
     * In the reference implementation, for strata which
     * do not explicitly specify source path (the Java
     * programming language stratum never does), the returned
     * string is the package name of {@link #declaringType()}
     * converted to a platform dependent path followed by the
     * unqualified name of the source file for this Location
     * ({@link #sourceName sourceName(stratum)}).
     * For example, on a
     * Windows platform, <CODE>java.lang.Thread</CODE>
     * would return
     * <CODE>"java\lang\Thread.java"</CODE>.
     *
     * @param stratum The stratum to retrieve information from
     * or <code>null</code> for the declaring type's
     * default stratum.
     *
     * @return a string specifying the source
     *
     * @throws AbsentInformationException if the source name is not
     * known
     *
     * @since 1.4
     */
    String sourcePath(String stratum)
                         throws AbsentInformationException;

    
Gets the line number of this Location.


This method is equivalent to
lineNumber(vm.getDefaultStratum()) - see lineNumber(String) for more information. 
Returns:an int specifying the line in the source, returns
-1 if the information is not available; specifically, always
returns -1 for native methods.
/**
     * Gets the line number of this Location.
     * <P>
     * This method is equivalent to
     * <code>lineNumber(vm.getDefaultStratum())</code> -
     * see {@link #lineNumber(String)}
     * for more information.
     *
     * @return an int specifying the line in the source, returns
     * -1 if the information is not available; specifically, always
     * returns -1 for native methods.
     */
    int lineNumber();

    
The line number of this Location. The line number is relative to the source specified by sourceName(stratum). 

Returned line number is for the specified stratum (see the class comment for a description of strata). 
Params:
  • stratum – The stratum to retrieve information from
or null for the declaring type's
default stratum.
Returns:an int specifying the line in the source, returns
-1 if the information is not available; specifically, always
returns -1 for native methods.
Since:1.4
/**
     * The line number of this Location.  The line number is
     * relative to the source specified by
     * {@link #sourceName(String) sourceName(stratum)}.
     * <P>
     * Returned line number is for the specified <i>stratum</i>
     * (see the {@link Location class comment} for a
     * description of strata).
     *
     * @param stratum The stratum to retrieve information from
     * or <code>null</code> for the declaring type's
     * default stratum.
     *
     * @return an int specifying the line in the source, returns
     * -1 if the information is not available; specifically, always
     * returns -1 for native methods.
     *
     * @since 1.4
     */
    int lineNumber(String stratum);

    
Compares the specified Object with this Location for equality.

Returns:true if the Object is a Location and if it refers to
the same point in the same VM as this Location.
/**
     * Compares the specified Object with this Location for equality.
     *
     * @return true if the Object is a Location and if it refers to
     * the same point in the same VM as this Location.
     */
    boolean equals(Object obj);

    
Returns the hash code value for this Location.

Returns:the integer hash code
/**
     * Returns the hash code value for this Location.
     *
     * @return the integer hash code
     */
    int hashCode();
}