本文研究的主要是Java中finally和return的关系，具体介绍和实例如下所示。
1.try块中有System.exit(0)这样的语句，由于它是终止Java虚拟机JVM的，连JVM都停止了，所有都结束了，当然finally语句也不会被执行到。
2.其它情况下，finally语句都必然会被执行。因此可以在这里执行一些资源的释放操作。
（1）finally中的return会覆盖try/catch中的renturn。
（2）在finally中写return语句会有警告，因为它会阻止函数抛出异常，而改为正常返回。
package com.demo.test; public class FinallyAndReturn { private static void finallyAndTryReturn() { try { System.out.println("finallyAndTryReturn -> try"); return; } catch (Exception e) { System.out.println("finallyAndTryReturn -> catch"); } finally { System.out.println("finallyAndTryReturn -> finally"); } } private static void finallyAndCatchReturn() { try { System.out.println("finallyAndCatchReturn -> try"); throw new Exception(); } catch (Exception e) { System.out.println("finallyAndCatchReturn -> catch"); return; } finally { System.out.println("finallyAndCatchReturn -> finally"); } } // finally语句是在try的return语句执行之后，return返回之前执行。 private static String tryReturn() { String str = "initialized"; try { System.out.println("tryReturn -> try"); str = "try"; return str; } catch (Exception e) { System.out.println("tryReturn -> catch"); str = "catch"; } finally { System.out.println("tryReturn -> finally"); str = "finally"; } return null; } private static String tryReturnAndFinallyReturn() { String str = "initialized"; try { System.out.println("tryReturnAndFinallyReturn -> try"); str = "try"; return str; } catch (Exception e) { System.out.println("tryReturnAndFinallyReturn -> catch"); str = "catch"; } finally { System.out.println("tryReturnAndFinallyReturn -> finally"); /* * Warning: finally block does not complete normally * 如果finally块中包含了return语句，即使前面的catch块重新抛出了异常，则调用该方法的语句也不会获得catch块重新抛出的异常，而是会得到finally块的返回值，并且不会捕获异常。 */ str = "finally"; return str; } } private static String tryThrowAndFinallyReturn() throws Exception { String str = "initialized"; try { System.out.println("tryThrowAndFinallyReturn -> try"); str = "try"; throw new Exception(); } catch (Exception e) { System.out.println("tryThrowAndFinallyReturn -> catch"); str = "catch"; throw new Exception(); } finally { System.out.println("tryThrowAndFinallyReturn -> finally"); /* * Warning: finally block does not complete normally * 如果finally块中包含了return语句，即使前面的catch块重新抛出了异常，则调用该方法的语句也不会获得catch块重新抛出的异常，而是会得到finally块的返回值，并且不会捕获异常。 */ str = "finally"; return str; } } private static void finallyAndRuntimeException() { try { System.out.println("finallyAndRuntimeException -> try"); throw new RuntimeException(); } catch (Exception e) { System.out.println("finallyAndRuntimeException -> catch"); } finally { System.out.println("finallyAndRuntimeException -> finally"); } } private static void finallyAndExit() { try { System.out.println("finallyAndExit -> try"); // System.exit(0);是终止Java虚拟机JVM的，连JVM都停止了，所有都结束了，当然finally语句也不会被执行到。 System.exit(0); } catch (Exception e) { System.out.println("finallyAndExit -> catch"); } finally { System.out.println("finallyAndExit -> finally"); } } public static void main(String[] args) { finallyAndTryReturn(); System.out.println(); finallyAndCatchReturn(); System.out.println(); System.out.println("tryReturn return -> " + tryReturn()); System.out.println(); System.out.println("tryReturnAndFinallyReturn return -> " + tryReturnAndFinallyReturn()); System.out.println(); try { System.out.println("tryThrowAndFinallyReturn return -> " + tryThrowAndFinallyReturn()); } catch (Exception e) { e.printStackTrace(); } System.out.println(); finallyAndRuntimeException(); System.out.println(); finallyAndExit(); } } 演示结果：
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