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JAVA代碼如下: [java] package com.test1; public class ReferencedCls { private String str = "test value"; public String getStr() { return str; } public void setStr(String str) { this.str = str; } public ReferencedCls() { System.out.println("Constructor: ReferencedCls"); } } package com.test2; import com.test1.ReferencedCls; public class StaticReferencingCls { public static void main(String[] args) { System.out.println("Started testing static loading..............."); ReferencedCls cls = new ReferencedCls(); System.out.println(cls.getStr()); } } package com.test2; import com.test1.ReferencedCls; public class DynamicReferencingCls { public static void main(String[] args) throws ClassNotFoundException, InstantiationException, IllegalAccessException { System.out.println("Started testing dynamic loading..............."); Class cls = Class.forName("com.test1.ReferencedCls"); ReferencedCls obj = (ReferencedCls)cls.newInstance(); System.out.println(obj.getStr()); } } 以不同的方式運(yùn)行: 1,在運(yùn)行環(huán)境中能找到需要的類時(shí),都正常運(yùn)行 [java] D:\>java -cp d:/temp/t1.jar;d:/temp/t2.jar com.test2.StaticReferencingCls Started testing static loading............... Constructor: ReferencedCls test value D:\>java -cp d:/temp/t1.jar;d:/temp/t2.jar com.test2.DynamicReferencingCls Started testing dynamic loading............... Constructor: ReferencedCls test value 2,以靜態(tài)方式加載,運(yùn)行環(huán)境缺失需要的類,拋出NoClassDefFoundError [java] D:\>java -cp d:/temp/t2.jar com.test2.StaticReferencingCls Started testing static loading............... Exception in thread "main" java.lang.NoClassDefFoundError: com/test1/ReferencedCls at com.test2.StaticReferencingCls.main(StaticReferencingCls.java:9) Caused by: java.lang.ClassNotFoundException: com.test1.ReferencedCls at java.net.URLClassLoader$1.run(Unknown Source) at java.security.AccessController.doPrivileged(Native Method) at java.net.URLClassLoader.findClass(Unknown Source) at java.lang.ClassLoader.loadClass(Unknown Source) at sun.misc.Launcher$AppClassLoader.loadClass(Unknown Source) at java.lang.ClassLoader.loadClass(Unknown Source) at java.lang.ClassLoader.loadClassInternal(Unknown Source) ... 1 more 3,以動態(tài)方式加載,運(yùn)行環(huán)境缺失需要的類,拋出ClassNotFoundException,同時(shí)在寫代碼的時(shí)候也需要catch這個(gè)異?；蛘呗暶鬟@個(gè)異常. [java] D:\>java -cp d:/temp/t2.jar com.test2.DynamicReferencingCls Started testing dynamic loading............... Exception in thread "main" java.lang.ClassNotFoundException: com.test1.ReferencedCls at java.net.URLClassLoader$1.run(Unknown Source) at java.security.AccessController.doPrivileged(Native Method) at java.net.URLClassLoader.findClass(Unknown Source) at java.lang.ClassLoader.loadClass(Unknown Source) at sun.misc.Launcher$AppClassLoader.loadClass(Unknown Source) at java.lang.ClassLoader.loadClass(Unknown Source) at java.lang.ClassLoader.loadClassInternal(Unknown Source) at java.lang.Class.forName0(Native Method) at java.lang.Class.forName(Unknown Source) at com.test2.DynamicReferencingCls.main(DynamicReferencingCls.java:11) 4,JVM本身使用的方式也是靜態(tài)加載,如用JAVA命令運(yùn)行一個(gè)帶main方法的類,這個(gè)類在運(yùn)行環(huán)境缺失. [java] D:\>java com.test2.XXXCls Exception in thread "main" java.lang.NoClassDefFoundError: com/test2/XXXCls Caused by: java.lang.ClassNotFoundException: com.test2.XXXCls at java.net.URLClassLoader$1.run(Unknown Source) at java.security.AccessController.doPrivileged(Native Method) at java.net.URLClassLoader.findClass(Unknown Source) at java.lang.ClassLoader.loadClass(Unknown Source) at sun.misc.Launcher$AppClassLoader.loadClass(Unknown Source) at java.lang.ClassLoader.loadClass(Unknown Source) at java.lang.ClassLoader.loadClassInternal(Unknown Source) Could not find the main class: com.test2.XXXCls. Program will exit. |
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