构造器异常处理
某些单例模式中的实例需要通过外部资源，如文件，jndi对象进行初始化。
此时可能出现初始化异常，而构造器中不能抛出异常，因此需通过标志位等其它方式进行处理。
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果断上代码，有码有真相
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1.实例
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package com.siyuan.jdktest;
import java.io.fileinputstream;<br>import java.io.filenotfoundexception;
public class constructorexptest {<br>?<br>?private static constructorexptest instance;<br>?<br>?private static boolean inited;<br>?<br>?private static initexception initexp;<br>?<br>?private constructorexptest(string path) {<br>??try {<br>???init(path);<br>???inited = true;<br>??} catch (initexception e) {<br>???initexp = e;<br>??}<br>?}<br>?<br>?private void init(string path) throws initexception {<br>???try {<br>????fileinputstream finput = new fileinputstream(path);<br>???} catch (filenotfoundexception e) {<br>????throw new initexception("error in constructorexptest init...", e);<br>???}
?}<br>?<br>?public static final constructorexptest getinstance(string path) throws initexception{<br>??if (instance == null) {<br>???instance = new constructorexptest(path);<br>??}<br>??if (!inited) {<br>???throw initexp;<br>??}<br>??return instance;<br>?}<br>?<br>?/**<br>? * @param args<br>? * @throws initexception <br>? */<br>?public static void main(string[] args) throws initexception {<br>??// todo auto-generated method stub<br>??system.out.println(constructorexptest.getinstance("asdfs"));<br>?}
}
class initexception extends exception {<br>?<br>?public initexception() {<br>??<br>?}<br>?<br>?public initexception(string msg) {<br>??super(msg);<br>?}<br>?<br>?public initexception(throwable cause) {<br>??super(cause);<br>?}
?public initexception(string msg, throwable cause) {<br>??super(msg, cause);<br>?}<br>?<br>}
