Guava – Throwables 类

Throwables类提供了与Throwable接口相关的实用方法

Throwables 类声明

以下是 com.google.common.base.Throwables 类的声明 −

public final class Throwables
   extends Object

Throwables 类函数

Sr.No	Method & Description
1	`static List<Throwable> getCausalChain(Throwable throwable)` 获取一个Throwable原因链，作为一个列表.
2	`static Throwable getRootCause(Throwable throwable)` 返回throwable的最内部原因.
3	`static String getStackTraceAsString(Throwable throwable)` 返回一个包含toString()结果的字符串，后面是完整的、递归的、throwable堆栈跟踪.
4	`static RuntimeException propagate(Throwable throwable)` 如果throwable是RuntimeException或Error的实例，则按原样传播，否则作为最后手段，将其包装成RuntimeException，然后传播.
5	`static <X extends Throwable> void propagateIfInstanceOf(Throwable throwable, Class<X> declaredType)` 当且仅当它是 declaredType 的一个实例时，完全按原样传播 throwable.
6	`static void propagateIfPossible(Throwable throwable)` 当且仅当它是RuntimeException或Error的实例时，完全按原样传播throwable.
7	`static <X extends Throwable> void propagateIfPossible(Throwable throwable, Class<X> declaredType)` 当且仅当它是RuntimeException、Error或diledType的实例时，完全按原样传播throwable.
8	`static <X1 extends Throwable,X2 extends Throwable>void propagateIfPossible(Throwable throwable, Class<X1> declaredType1, Class<X2> declaredType2)` 当且仅当它是RuntimeException、Error、predatedType1或predatedType2的实例时，才会完全按原样传播throwable.

Throwables 类继承

该类继承了以下类的方法 −

java.lang.Object

Throwables 类示例

在C:/>Guava中使用你选择的任何编辑器创建以下java程序

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 {
}

Throwables 类验证结果

使用javac编译器编译该类，如下所示 −

C:\Guava>javac GuavaTester.java

现在运行GuavaTester来看看结果.

C:\Guava>java GuavaTester

查看结果.

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