Java类库实践点滴—— Logging、Object、assert

<script type="text/javascript" src="http://pagead2.googlesyndication.com/pagead/show_ads.js"> </script> Java类库实践点滴（一） —— Logging、Object、assert 一、java.util.Logging: 例子： //测试Java1.4中的日志新功能import java.util.logging.*;public class TestLogging { //设置logger static Logger testLog = Logger.getLogger("test.log"); public static void main(String[] args) { //测试Warn级别的日志 testLog.warning("sample warning"); //测试所有级别 //缺省在控制台上显示 SEVERE, WARNING, INFO级别的日志 testLog.log(Level.SEVERE, "severe log"); testLog.log(Level.WARNING, "warning log"); testLog.log(Level.INFO, "info log"); testLog.log(Level.CONFIG, "config log"); testLog.log(Level.FINE, "fine log"); testLog.log(Level.FINER, "finer log"); testLog.log(Level.FINEST, "finest log"); testLog.log(Level.ALL, "all log"); }} 输出： Oct 14, 2003 10:33:18 AM TestLogging main WARNING: sample warning Oct 14, 2003 10:33:18 AM TestLogging main SEVERE: severe log Oct 14, 2003 10:33:18 AM TestLogging main WARNING: warning log Oct 14, 2002 10:33:18 AM TestLogging main INFO: info log 二、java.lang.Object类 首先需要注意: 1. 每一个class扩展自Object 2. 不能在Object变量中存储基本类型 Object objStringFive = new String("5"); //可以执行Object objDoubleFive = new Double("5"); //可以执行 int fiver = 5;Object objFive = fiver; //编译不通过Object anotherObjFive = 5; //编译不通过 常用的Object的方法: Object cloneOfObject = objectToClone.clone();boolean isEqual = objectToCompare.equals(objectToCompareTo);Class runtimeClass = objectToGetClassFrom.getClass();int hashCodeOfObject = objectToGetHashCodeOf.hashCode();String stringValue = objectToGetStringOf.toString(); 常用的线程的对象方法: objectWithThreadWaiting.notify();//唤醒当前线程objectWithThreadWaiting.notifyAll();//唤醒所有线程objectToMakeThreadWait.wait();//线程一直处于sleep状态，直到出现 notify()或 notifyAll()为止objectToMakeThreadWait.wait(longTimeToWaitInMilliseconds);//当前线程一直处于sleep状态，直到出现notify(), notifyAll(), //或过了longTimeToWaitInMilliseconds秒延迟之后为止objectToMakeThreadWait.wait(longTimeToWaitInMilliseconds, intTimeToWaitInNanoseconds);//当前线程一直处于sleep状态，直到出现notify(), notifyAll(), //或longTimeToWaitInMilliseconds intTimeToWaitInNanoseconds 秒延迟之后为止 垃圾收集的对象方法： objectForGarbageCollection.finalize();//当没有对象引用存在时，执行垃圾收集 三、 断言的基本使用 //jdk1.4 中的新的assert 语句和关键字// 用 -source 作为1.4 编译的标志// 用 -ea 标志来运行public class TestAssertions { static boolean goodHalOpen = true; static boolean badHalOpen = false; static boolean openPodDoor = false; //设置断言 static void testPodDoor() { /*注意: 在assert语句中，如果冒号之前的表达式等于false，那么 就抛出异常java.lang.AssertionError 当抛出AssertionError时，将输出冒号之后的表达式的文本。 */ assert openPodDoor : "bad Hal"; System.out.println("after assertion"); System.out.println(" "); } public static void main(String[] args) { System.out.println("test one"); openPodDoor = goodHalOpen; testPodDoor(); System.out.println("test two"); openPodDoor = badHalOpen; testPodDoor(); }} 编译和运行: javac -source 1.4 TestAssertions.java java -ea TestAssertions 输出: test one after assertion test two Exception in thread "main" java.lang.AssertionError: bad Hal at TestAssertions.testPodDoor(TestAssertions.java:19) at TestAssertions.main(TestAssertions.java:33)