项目中捕获异常的优化

</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
*/
@Slf4j
public 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