异常

所有的异常都是继承Throwable

抛个自定义的异常

var l = listOf("1", "a", "b", "c", "d", "e")
    if (l.size < 19) throw Throwable("FUCK YOU!", Throwable("这是原因 list 长度必须 大于19."))
/**
java.lang.Throwable: FUCK YOU!

    at coin.otc.com.otc.kotlin.BaseSyntaxKt.BaseMain(BaseSyntax.kt:27)
    at coin.otc.com.otc.kotlin.MainKt.TestMain(Main.kt:10)
    at coin.otc.com.otc.ExampleUnitTest.Main(ExampleUnitTest.java:16)
    at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
    at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
    at java.lang.reflect.Method.invoke(Method.java:498)
    at org.junit.runners.model.FrameworkMethod$1.runReflectiveCall(FrameworkMethod.java:50)
    at org.junit.internal.runners.model.ReflectiveCallable.run(ReflectiveCallable.java:12)
    at org.junit.runners.model.FrameworkMethod.invokeExplosively(FrameworkMethod.java:47)
    at org.junit.internal.runners.statements.InvokeMethod.evaluate(InvokeMethod.java:17)
    at org.junit.runners.ParentRunner.runLeaf(ParentRunner.java:325)
    at org.junit.runners.BlockJUnit4ClassRunner.runChild(BlockJUnit4ClassRunner.java:78)
    at org.junit.runners.BlockJUnit4ClassRunner.runChild(BlockJUnit4ClassRunner.java:57)
    at org.junit.runners.ParentRunner$3.run(ParentRunner.java:290)
    at org.junit.runners.ParentRunner$1.schedule(ParentRunner.java:71)
    at org.junit.runners.ParentRunner.runChildren(ParentRunner.java:288)
    at org.junit.runners.ParentRunner.access$000(ParentRunner.java:58)
    at org.junit.runners.ParentRunner$2.evaluate(ParentRunner.java:268)
    at org.junit.runners.ParentRunner.run(ParentRunner.java:363)
    at org.junit.runner.JUnitCore.run(JUnitCore.java:137)
    at com.intellij.junit4.JUnit4IdeaTestRunner.startRunnerWithArgs(JUnit4IdeaTestRunner.java:68)
    at com.intellij.rt.execution.junit.IdeaTestRunner$Repeater.startRunnerWithArgs(IdeaTestRunner.java:47)
    at com.intellij.rt.execution.junit.JUnitStarter.prepareStreamsAndStart(JUnitStarter.java:242)
    at com.intellij.rt.execution.junit.JUnitStarter.main(JUnitStarter.java:70)
    at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
    at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
    at java.lang.reflect.Method.invoke(Method.java:498)
    at com.intellij.rt.execution.application.AppMainV2.main(AppMainV2.java:131)
Caused by: java.lang.Throwable: 这是原因 list 长度必须 大于19.
    ... 30 more

*/

处理异常 try catch finally 语句

  try {
        if (l.size < 19) throw Throwable("FUCK YOU!", Throwable("这是原因 list 长度必须 大于19."))
    } catch (e: Exception) {
        println("This is error: $e")
    } finally {
    }

try 表达式

try 和catch 可以有返回值，但是不知道为什么 catch 后没有获取值。

  var l = listOf("1", "a", "b", "c", "d", "e")

    var num: Int? = try {
        if (l.size < 1) throw Throwable("FUCK YOU!", Throwable("这是原因 list 长度必须 大于19."))
        1
    } catch (e: Exception) {
        null
    }
    println("num is $num")