解讀java.lang.Class

public final class Class {     private Class() {}     public static native Class forName(String className) throws            ClassNotFoundException;     public native Object newInstance() throws InstantiationException,            IllegalAccessException;     public native boolean isInstance(Object obj);     public native boolean isAssignableFrom(Class cls);     public native boolean isInte***ce();     public native boolean isArray();     public native String getName();     public Java.io.InputStream getResourceAsStream(String name) {        try {            if (name.length() > 0 && name.charAt(0) == '/') {                name = name.substring(1);            } else {                String className = this
   .getName(); int dotIndex = className.lastIndexOf('.'); if (dotIndex >= 0) { name = className.substring(0, dotIndex + 1).replace('.', '/') + name; } } return new ResourceInputStream(name); } catch (Java.io.IOException x) { return null; } }  private static void runCustomCode() {}  private native Class getSuperclass();  private transIEnt Object vmClass; private int status; private Thread thread; private static final int VERIFIED = 1; private static final int IN_PROGRESS = 2; private static final int INITIALIZED = 3; private static final int ERROR = 4; private native void invoke_clinit();  private native void invoke_verifIEr();  void initialize() throws Throwable { verify(); synchronized (this) { while (status == IN_PROGRESS && thread != Thread.currentThread()) { try { wait(); } catch (InterruptedException e) {} } if (status == IN_PROGRESS && thread == Thread.currentThread()) { return; } if (status == INITIALIZED) { return; } if (status == ERROR) { throw new Error("NoClassDefFoundError:" + getName()); } status = IN_PROGRESS; thread = Thread.currentThread(); }  try {  Class s = getSuperclass(); if (s != null && s.status

!= INITIALIZED) { s.initialize(); } invoke_clinit(); synchronized (this) { status = INITIALIZED; thread = null; notifyAll(); } } catch (Throwable e) {  synchronized (this) { status = ERROR; thread = null; notifyAll(); throwError(e); } } }  synchronized void verify() throws Throwable { if (status < VERIFIED) { getSuperclass().verify(); invoke_verifIEr(); status = VERIFIED; } }  private Error throwError(Throwable e) throws Error { throw (e instanceof Error) ? (Error) e : new Error("Static initializer: " + e.getClass().getName

() + ", " + e.getMessage()); }}

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為什麼private Class()呢？由於class是需要編譯好的class文件。當然，現在有技巧將代碼編譯成class文件。forName()：從.class文件裝載並創立Class。Class是object的結構信息呀。但J2ME的才能有限，你不能獲取該class有多少個字段，多少個方法。留心：J2ME裡面沒有ClassLoader。但是，通過另外方法來處理ClassLoader了，從上面可以看出，每次Class裝載需要兩部：init和verify。class裝載的次序呢，當然首先是系統，然後就是用戶的了。由於JVM每次只跑一個MIDlet，所以並沒有復雜的依附關系了。