Java-Class Library-Guava-Throwables Class

Sometimes, when we catch an exception, we pass the exception to the next try/catch block. Guava provides an exception handling utility class that can simply catch and rethrow multiple exceptions.

[code]import java.io.IOException;
import org.junit.Test;
import com.google.common.base.Throwables;

public class ThrowablesTest {

    @Test
    public void testThrowables(){
        try {
            throw new Exception();
        } catch (Throwable t) {
            String ss = Throwables.getStackTraceAsString(t);
            System.out.println("ss:"+ss);
            Throwables.propagate(t);
        }
    }

    @Test
    public void call() throws IOException {
        try {
            throw new IOException();
        } catch (Throwable t) {
            Throwables.propagateIfInstanceOf(t, IOException.class);
            throw Throwables.propagate(t);
        }
    }    
}

Convert checked exceptions into unchecked exceptions, for example:

[code]import java.io.InputStream;
import java.net.URL;
import org.junit.Test;
import com.google.common.base.Throwables;

public class ThrowablesTest {

    @Test
    public void testCheckException(){
        try {  
            URL url = new URL("http://ociweb.com");  
            final InputStream in = url.openStream();  
            // read from the input stream  
            in.close();  
        } catch (Throwable t) {  
            throw Throwables.propagate(t);  
        }  
    }
}

Common methods of passing exceptions:

1.RuntimeException propagate(Throwable): wrap throwable into RuntimeException , use this method to ensure exception delivery and throw a RuntimeException

2.void propagateIfInstanceOf(Throwable, Class) throws X: If and only if it is an instance of X, pass throwable

　3.void propagateIfPossible(Throwable): If and only if it is a RuntimeException and Error, pass throwable

　4.void propagateIfPossible(Throwable, Class) throws X: If and only if it is a RuntimeException and Error, or an instance of X, pass throwable.

[code]import java.io.IOException;
import org.junit.Test;
import com.google.common.base.Throwables;

public class ThrowablesTest {    
    @Test
    public void testThrowables(){
        try {
            throw new Exception();
        } catch (Throwable t) {
            String ss = Throwables.getStackTraceAsString(t);
            System.out.println("ss:"+ss);
            Throwables.propagate(t);
        }
    }

    @Test
    public void call() throws IOException {
        try {
            throw new IOException();
        } catch (Throwable t) {
            Throwables.propagateIfInstanceOf(t, IOException.class);
            throw Throwables.propagate(t);
        }
    }

    public Void testPropagateIfPossible() throws Exception {
          try {
              throw new Exception();
          } catch (Throwable t) {
            Throwables.propagateIfPossible(t, Exception.class);
            Throwables.propagate(t);
          }

          return null;
    }
}

Guava’s exception chain handling method:

1.Throwable getRootCause(Throwable)

2.List getCausalChain(Throwable)

3.String getStackTraceAsString (Throwable)

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