System类的out对象是什么时候在Java中初始化的？

Question

修改为final的变量必须在声明或执行构造函数时初始化。

我在系统类文件中查找，发现out对象是在私有静态void initializeSystemClass()方法中初始化的，什么时候调用这个方法？

Answer 1

这个方法由JVM根据System类中的注释调用。添加以下评论部分：

public final class System {

    /* 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();
    }

    /** Don't let anyone instantiate this class */
    private System() {
    }