Java.lang.StackTraceElement class in Java

An element in a stack trace, as returned by Throwable.getStackTrace(). Each element represents a single stack frame. All stack frames except for the one at the top of the stack represent a method invocation. The frame at the top of the stack represents the execution point at which the stack trace was generated. 

This class describes single stack frame, which is an individual element of a stack trace when an exception occur.

• All stack frames except for the one at the top of the stack represent a method invocation.
• The frame at the top of the stack represent the execution point of which the stack trace was generated.
• Each stack frame represents an execution point, which includes such things as the name of the method, the name of file and the source code line number.
• An array of StackTraceElement is returned by getStackTrace()
  method of the Throwable class.

Constructor: Creates a stack trace element representing the specified execution point.

StackTraceElement(String declaringClass, 
String methodName, String fileName, int lineNumber)

Parameters: 

• declaringClass – the fully qualified name of the class containing the execution point represented by the stack trace element.
• methodName – the name of the method containing the execution point represented by the stack trace element.
• fileName – the name of the file containing the execution point represented by the stack trace element, or null if this information is unavailable
• lineNumber – the line number of the source line containing the execution point represented by this stack trace element, or a negative number if this information is unavailable. A value of -2 indicates that the method containing the execution point is a native method.

Throws: NullPointerException – if declaringClass or methodName is null.

Methods: 

1. boolean equals(ob): Returns try if the invoking StackTraceElement is as the one passed in ob. Otherwise it returns false.

Syntax: public boolean equals(ob)
Returns: true if the specified object is 
another StackTraceElement instance representing the same execution 
point as this instance.
Exception: NA

Java

// Java code illustrating equals() method
import java.lang.*;
import java.io.*;
import java.util.*;
public class StackTraceElementDemo
{
    public static void main(String[] arg)
    {
        StackTraceElement st1 = new StackTraceElement("foo", "fuction1",
                                                   "StackTrace.java", 1);
        StackTraceElement st2 = new StackTraceElement("bar", "function2",
                                                   "StackTrace.java", 1);

        Object ob = st1.getFileName();

        // checking whether file names are same or not
        System.out.println(st2.getFileName().equals(ob));
    }
}

Output:

true

2. String getClassName(): Returns the class name of the execution point described by the invoking StackTraceElement.

Syntax: public String getClassName().
Returns: the fully qualified name of the Class
containing the execution point represented by this stack trace element.
Exception: NA.

Java

// Java code illustrating getClassName() method.
import java.lang.*;
import java.io.*;
import java.util.*;
public class StackTraceElementDemo
{
    public static void main(String[] arg)
    {
        System.out.println("Class name of each thread involved:");
        for(int i = 0; i<2; i++)
        {
            System.out.println(Thread.currentThread().getStackTrace()[I].
            getClassName());
        }
    }
}

Output:

Class name of each thread involved:
java.lang.Thread
StackTraceElementDemo

3. String getFileName(): Returns the file name of the execution point described by the invoking StackTraceElement.

Syntax: public String getFileName().
Returns: the name of the file containing 
the execution point represented by this stack trace element,
or null if this information is unavailable.
Exception: NA.

Java

// Java code illustrating getFileName() method.
import java.lang.*;
import java.io.*;
import java.util.*;
public class StackTraceElementDemo
{
   public static void main(String[] arg)
   {
       System.out.println("file name: ");
       for(int i = 0; i<2; i++)
       System.out.println(Thread.currentThread().getStackTrace()[i].
        getFileName());
   }
}

Output:

file name: 
Thread.java
StackTraceElementDemo.java

4. int getLineNumber(): Returns the source-code line number of the execution point described by the invoking StackTraceElement. In some situation the line number will not be available, in which case a negative value is returned.

Syntax: public int getLineNumber().
Returns: the line number of the source line 
containing the execution point represented by this stack 
trace element, or a negative number if this information is 
unavailable.
Exception: NA.

Java

// Java code illustrating getLineNumber() method.
import java.lang.*;
import java.io.*;
import java.util.*;
public class StackTraceElementDemo
{
   public static void main(String[] arg)
   {
       System.out.println("line number: ");
       for(int i = 0; i<2; i++)
       System.out.println(Thread.currentThread().getStackTrace()[i].
        getLineNumber());
   }
}

Output:

line number: 
1556
10

5. String getMethodName(): Returns the method name of the execution point described by the invoking StackTraceElement.

Syntax: public String getMethodName().
Returns: the name of the method containing the 
execution point represented by this stack trace element.
Exception: NA.

Java

// Java code illustrating getMethodName() method.
import java.lang.*;
import java.io.*;
import java.util.*;
public class StackTraceElementDemo
{
   public static void main(String[] arg)
   {
       System.out.println("method name: ");
       for(int i = 0; i<2; i++)
       System.out.println(Thread.currentThread().getStackTrace()[i].
        getMethodName());
   }
}

Output:

method name: 
getStackTrace
main

6. int hashCode(): Returns the hash code of the invoking StackTraceElement.

Syntax: public int hashCode().
Returns: a hash code value for this object.
Exception: NA.

Java

// Java code illustrating hashCode() method.
import java.lang.*;
import java.io.*;
import java.util.*;
public class StackTraceElementDemo
{
   public static void main(String[] arg)
   {
       System.out.println("hash code: ");
       for(int i = 0; i<2; i++)
       System.out.println(Thread.currentThread().getStackTrace()[i].
        hashCode());
   }
}

Output:

hash code: 
-1225537245
-1314176653

7. boolean isNativeMethod(): Returns true if the invoking StackTraceElement describes a native method. Otherwise returns false.

Syntax: public boolean isNativeMethod().
Returns: true if the method containing the execution 
point represented by this stack trace element is a native method.
Exception: NA.

Java

// Java code illustrating isNativeMethod() method.
import java.lang.*;
import java.io.*;
import java.util.*;
public class StackTraceElementDemo
{
   public static void main(String[] arg)
   {

       for(int i = 0; i<2; i++)
       System.out.println(Thread.currentThread().getStackTrace()[i].
        isNativeMethod());
   }
}

Output:

false
false

8. String toString(): Returns the String equivalent of the invoking sequence.

Syntax: public String toString().
Returns: a string representation of the object.
Exception: NA.

Java

// Java code illustrating toString() method.
import java.lang.*;
import java.io.*;
import java.util.*;
public class StackTraceElementDemo
{
   public static void main(String[] arg)
   {
       System.out.println("String equivalent: ");
       for(int i = 0; i<2; i++)
       System.out.println(Thread.currentThread().getStackTrace()[i].
        toString());
   }
}

Output:

String equivalent: 
java.lang.Thread.getStackTrace
StackTraceElementDemo.main