RunnableChain.java

package org.threadly.concurrent;

import java.util.Collections;
import java.util.Iterator;

import org.threadly.util.ExceptionUtils;

/**
 * A class to chain multiple runnables to later be run together, within the same thread.
 * 
 * @since 1.0.0
 */
public class RunnableChain implements Runnable {
  protected final boolean exceptionStopsChain;
  private final Iterable<? extends Runnable> toRun;
  
  /**
   * Constructs a runnable chain with a provided list of runnables to iterate over.
   * 
   * @param exceptionStopsChain {@code true} for uncaught exception stops the execution of the chain
   * @param toRun Iterable collection of runnables to run
   */
  public RunnableChain(boolean exceptionStopsChain, 
                       Iterable<? extends Runnable> toRun) {
    if (toRun == null) {
      toRun = Collections.emptyList();
    }
    
    this.exceptionStopsChain = exceptionStopsChain;
    this.toRun = toRun;
  }

  @Override
  public void run() {
    if (exceptionStopsChain) {
      runExceptionsCascade();
    } else {
      runIsolated();
    }
  }
  
  /**
   * Iterates through the toRun list, executing along the way.  If any exceptions are thrown, they 
   * will be propagated out of this call.
   */
  protected void runExceptionsCascade() {
    Iterator<? extends Runnable> it = toRun.iterator();
    while (it.hasNext()) {
      it.next().run();
    }
  }
  
  /**
   * Iterates through the toRun list, executing along the way.  If any exceptions are thrown, they 
   * will be handled to {@link ExceptionUtils} and will not stop future executions.
   */
  protected void runIsolated() {
    Iterator<? extends Runnable> it = toRun.iterator();
    while (it.hasNext()) {
      ExceptionUtils.runRunnable(it.next());
    }
  }
}