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package com.windofkeltia.stack_parent;

import java.lang.invoke.MethodHandles;
import java.util.ArrayList;
import java.util.Collections;
import java.util.List;

import static java.util.Objects.isNull;
import static java.util.Objects.nonNull;

/**
 * StackWalker is a Java 9 construct; it doesn't exist
 * in Java 8. Here's a quick, but plausible replacement for just
 * the functionality of getting the parent's classname, full
 * classname or method name.
 * @author Russell Bateman
 * @since October 2019
 */
public class StackParent
{
  private List< String > skipThese = new ArrayList<>();

  /**
   * Construct this utility to skip over stuff we happen not
   * to want to count in looking for a parent caller.
   * @param skipMe any number of classes to skip over by full package- and classname.
   */
  public StackParent( final String ... skipMe )
  {
    Collections.addAll( skipThese, skipMe );

    Class clazz = MethodHandles.lookup().lookupClass();
    skipThese.add( clazz.getName() );   // skip over this utility!
    skipThese.add( "java.lang.Thread" );
  }

  /**
   * See {@link #getParentMethod( String )} as if null is passed.
   */
  public String getParentMethod()
  {
    StackTraceElement parent = getParent();
    return( nonNull( parent ) ) ? parent.getMethodName() : null;
  }

  /**
   * See {@link #getParentFullClass( String )} as if null is passed.
   */
  public String getParentFullClass()
  {
    StackTraceElement parent = getParent();
    return( nonNull( parent ) ) ? parent.getClassName() : null;
  }

  /**
   * See {@link #getParentClass( String )} as if null is passed.
   */
  public String getParentClass()
  {
    String classPath = getParentFullClass();

    if( isNull( classPath ) )
      return null;

    String[] elements = classPath.split( "[.]" );
    return elements[ elements.length-1 ];
  }

  /**
   * Return the method name in the first class on the stack containing
   * the passed string. If only wanting the immediate caller no matter
   * what the name or package name, set MUST_BE_CONTAINED to null.
   * @param MUST_BE_CONTAINED string that helps reject names we're not looking for.
   * @return parent-method name.
   */
  public String getParentMethod( final String MUST_BE_CONTAINED )
  {
    StackTraceElement parent = getParent( MUST_BE_CONTAINED );
    return( nonNull( parent ) ) ? parent.getMethodName() : null;
  }

  /**
   * Return the full package name of the first class on the stack containing
   * the passed string. If only wanting the immediate caller no matter
   * what the name or package name, set MUST_BE_CONTAINED to null.
   * @param MUST_BE_CONTAINED string that helps reject names we're not looking for.
   * @return parent class' full name including package.
   */
  public String getParentFullClass( final String MUST_BE_CONTAINED )
  {
    StackTraceElement parent = getParent( MUST_BE_CONTAINED );
    return( nonNull( parent ) ) ? parent.getClassName() : null;
  }

  /**
   * Return the simple name of the first class on the stack containing
   * the passed string (in its package or simple name). If only wanting
   * the immediate caller no matter what the name or package name, set
   * MUST_BE_CONTAINED to null.
   * @param MUST_BE_CONTAINED string that helps reject names we're not looking for.
   * @return parent class' name alone devoid of package path.
   */
  public String getParentClass( final String MUST_BE_CONTAINED )
  {
    String classPath = getParentFullClass( MUST_BE_CONTAINED );

    if( isNull( classPath ) )
      return null;

    String[] elements = classPath.split( "[.]" );
    return elements[ elements.length-1 ];
  }

  /** (Heavy lifting...) */
  private StackTraceElement getParent()
  {
    StackTraceElement[] stackTraceElements = Thread.currentThread().getStackTrace();

    for( StackTraceElement element : stackTraceElements )
    {
      String FULLCLASS = element.getClassName();

      if( skipThese.contains( FULLCLASS ) )
        continue;

      return element;
    }

    return null;
  }

  /** (Heavy lifting...) */
  private StackTraceElement getParent( final String MUST_BE_CONTAINED )
  {
    StackTraceElement[] stackTraceElements = Thread.currentThread().getStackTrace();

    for( StackTraceElement element : stackTraceElements )
    {
      String FULLCLASS = element.getClassName();

      if( skipThese.contains( FULLCLASS ) )
        continue;

      // extra zeroing in: look for package/classname with 'MUST_BE_CONTAINED' in it...
      final String CLASSNAME = element.getClassName();

      if( CLASSNAME.contains( MUST_BE_CONTAINED ) )
        return element;
    }

    return null;
  }
}

package com.windofkeltia.stack_parent;

import org.junit.Test;

public class StackParentTest
{
  @Test
  public void test()
  {
    StackParent stackParent = new StackParent();
    System.out.println( "  Parent path:   " + stackParent.getParentFullClass() );
    System.out.println( "  Parent class:  " + stackParent.getParentClass() );
    System.out.println( "  Parent method: " + stackParent.getParentMethod() );
  }
}

  Parent path:   com.windofkeltia.stack_parent.StackParentTest
  Parent class:  StackParentTest
  Parent method: test