Table of Contents

Guava – Throwables Class

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Throwables class provides utility methods related to Throwable interface.

Class Declaration

Following is the declaration for com.google.common.base.Throwables class −

public final class Throwables
   extends Object

Class Methods

Sr.No	Method & Description
1	static List<Throwable> getCausalChain(Throwable throwable) Gets a Throwable cause chain as a list.
2	static Throwable getRootCause(Throwable throwable) Returns the innermost cause of throwable.
3	static String getStackTraceAsString(Throwable throwable) Returns a string containing the result of toString(), followed by the full, recursive stack trace of throwable.
4	static RuntimeException propagate(Throwable throwable) Propagates throwable as-is if it is an instance of RuntimeException or Error, or else as a last resort, wraps it in a RuntimeException then propagates.
5	static <X extends Throwable> void propagateIfInstanceOf(Throwable throwable, Class<X> declaredType) Propagates throwable exactly as-is, if and only if it is an instance of declaredType.
6	static void propagateIfPossible(Throwable throwable) Propagates throwable exactly as-is, if and only if it is an instance of RuntimeException or Error.
7	static <X extends Throwable> void propagateIfPossible(Throwable throwable, Class<X> declaredType) Propagates throwable exactly as-is, if and only if it is an instance of RuntimeException, Error, or declaredType.
8	static <X1 extends Throwable,X2 extends Throwable>void propagateIfPossible(Throwable throwable, Class<X1> declaredType1, Class<X2> declaredType2) Propagates throwable exactly as-is, if and only if it is an instance of RuntimeException, Error, declaredType1, or declaredType2.

Methods Inherited

This class inherits methods from the following class −

java.lang.Object

Example of Throwables Class

Create the following java program using any editor of your choice in say C:/> Guava.

GuavaTester.java

import java.io.IOException;

import com.google.common.base.Objects;
import com.google.common.base.Throwables;

public class GuavaTester {
   public static void main(String args[]) {
   
      GuavaTester tester = new GuavaTester();

      try {
         tester.showcaseThrowables();
         
      } catch (InvalidInputException e) {
         //get the root cause
         System.out.println(Throwables.getRootCause(e));
      
      } catch (Exception e) {
         //get the stack trace in string format
         System.out.println(Throwables.getStackTraceAsString(e));
      }

      try {
         tester.showcaseThrowables1();

      } catch (Exception e) {
         System.out.println(Throwables.getStackTraceAsString(e));
      }
   }

   public void showcaseThrowables() throws InvalidInputException {
      try {
         sqrt(-3.0);
      } catch (Throwable e) {
         //check the type of exception and throw it
         Throwables.propagateIfInstanceOf(e, InvalidInputException.class);
         Throwables.propagate(e);
      }
   }

   public void showcaseThrowables1() {
      try {
         int[] data = {1,2,3};
         getValue(data, 4);
      } catch (Throwable e) {
         Throwables.propagateIfInstanceOf(e, IndexOutOfBoundsException.class);
         Throwables.propagate(e);
      }
   }

   public double sqrt(double input) throws InvalidInputException {
      if(input < 0) throw new InvalidInputException();
      return Math.sqrt(input);
   }

   public double getValue(int[] list, int index) throws IndexOutOfBoundsException {
      return list[index];
   }

   public void dummyIO() throws IOException {
      throw new IOException();
   }
}

class InvalidInputException extends Exception {
}

Verify the Result

Compile the class using javac compiler as follows −

C:Guava>javac GuavaTester.java

Now run the GuavaTester to see the result.

C:Guava>java GuavaTester

See the result.

InvalidInputException
java.lang.ArrayIndexOutOfBoundsException: 4
   at GuavaTester.getValue(GuavaTester.java:52)
   at GuavaTester.showcaseThrowables1(GuavaTester.java:38)
   at GuavaTester.main(GuavaTester.java:19)

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