System.out.println(); 是刚学java就接触的东西, 但是有些东西到现在才开始思考
首先说out , System.out : 声明位置:
/** * The "standard" output stream. This stream is already * open and ready to accept output data. Typically this stream * corresponds to display output or another output destination * specified by the host environment or user. * <p> * For simple stand-alone Java applications, a typical way to write * a line of output data is: * <blockquote><pre> * System.out.println(data) * </pre></blockquote> * <p> * See the <code>println</code> methods in class <code>PrintStream</code>. * * @see java.io.PrintStream#println() * @see java.io.PrintStream#println(boolean) * @see java.io.PrintStream#println(char) * @see java.io.PrintStream#println(char[]) * @see java.io.PrintStream#println(double) * @see java.io.PrintStream#println(float) * @see java.io.PrintStream#println(int) * @see java.io.PrintStream#println(long) * @see java.io.PrintStream#println(java.lang.Object) * @see java.io.PrintStream#println(java.lang.String) */ public final static PrintStream out = null;常见的使用方式,在out的注解里都写了,这里就不多做赘述了.
这是jdk中System类的源码与注释, 可以看出这个out对象虽然为空,但是是在启动时就初始化好的, 其初始化位置为:
/* register the natives via the static initializer. * * VM will invoke the initializeSystemClass method to complete * the initialization for this class separated from clinit. * Note that to use properties set by the VM, see the constraints * described in the initializeSystemClass method. */ private static native void registerNatives(); static { registerNatives(); }可以明显的看出,该方法是native的 , 这样就不用继续看了,就到这里了,本地方法,就不一定是啥东西了
不过我还是想说一句:第三行最后一个单词clinit 这个单词到底是什么意思, 是写错了吗? 求大神留言
