项目中捕获异常的优化

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</pre>1、不用在循环中使用try()catch(); 每次捕获都需要消耗时间的</p><p></p><p>2、尽量捕获具体的异常类，不要用catch(Exception e)去替代所有的异常，因为jvm识别具体的异常是需要消耗时间的。</p><p></p><p><pre name="code" class="html">package com.team.gaoguangjin.javabase.exception;import java.io.File;import java.io.FileInputStream;import java.io.FileNotFoundException;import java.io.IOException;import lombok.extern.slf4j.Slf4j;/** *  * @author gaoguangjin 为什么不提倡catch(Exception) try..catch 在出现异常的时候影响性能; 应该捕获更具体得异常，比如IOExeception,OutOfMemoryException等 */@Slf4jpublic class ExceptionCapability {public static void main(String[] args) {exceptionByListTest();exectionCapabilityTest();}/** * 测试循环里面添加异常捕获 */private static void exceptionByListTest() {long time = System.currentTimeMillis();for (int i = 0; i < 100; i++) {catchExceptionTest();}long endTime = System.currentTimeMillis();long time2 = System.currentTimeMillis();try {for (int i = 0; i < 100; i++) {catchExceptionNormal();}}catch (Exception e) {log.error("捕获Exception：" + e.getLocalizedMessage());}long endTime2 = System.currentTimeMillis();log.info("catchExceptionTest花费时间：" + (endTime - time));log.info("catchNormallException花费时间：" + (endTime2 - time2));}private static void catchExceptionNormal() throws IOException {File file = new File("aa");FileInputStream fis = new FileInputStream(file);fis.close();}/** * 比较catch具体的异常类和直接异常的性能 catch(Excepiton e)和 catch(DetailExcepiton e)比较 *  */private static void exectionCapabilityTest() {long time = System.currentTimeMillis();for (int i = 0; i < 100; i++) {catchExceptionTest();}long endTime = System.currentTimeMillis();long time2 = System.currentTimeMillis();for (int i = 0; i < 100; i++) {catchDetailException();}long endTime2 = System.currentTimeMillis();log.info("catchExceptionTest花费时间：" + (endTime - time));log.info("catchDetailException花费时间：" + (endTime2 - time2));}private static void catchDetailException() {try {File file = new File("aa");FileInputStream fis = new FileInputStream(file);fis.close();}catch (FileNotFoundException e) {log.error("捕获FileNotFoundException：" + e.getLocalizedMessage());}catch (IOException e) {log.error("捕获IOException：" + e.getLocalizedMessage());}}private static void catchExceptionTest() {try {File file = new File("aa");FileInputStream fis = new FileInputStream(file);fis.close();}catch (Exception e) {log.error("捕获Exception：" + e.getLocalizedMessage());}}}

2015-1-16 9:48:13 com.team.gaoguangjin.javabase.exception.ExceptionCapability exectionCapabilityTest
信息: catchExceptionTest花费时间：355
2015-1-16 9:48:13 com.team.gaoguangjin.javabase.exception.ExceptionCapability exectionCapabilityTest

信息: catchDetailException花费时间：15

2015-1-16 10:17:03 com.team.gaoguangjin.javabase.exception.ExceptionCapability exceptionByListTest
信息: catchExceptionTest花费时间：30
2015-1-16 10:17:03 com.team.gaoguangjin.javabase.exception.ExceptionCapability exceptionByListTest
信息: catchExceptionNormal花费时间：1

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