native 方法的源码有关问题

/* * Copyright (C) 2006 The Android Open Source Project * * Licensed under the Apache License, Version 2.0 (the "License"); * you may not use this file except in compliance with the License. * You may obtain a copy of the License at * *      http://www.apache.org/licenses/LICENSE-2.0 * * Unless required by applicable law or agreed to in writing, software * distributed under the License is distributed on an "AS IS" BASIS, * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. * See the License for the specific language governing permissions and * limitations under the License. */package android.graphics;public class Camera {    public Camera() {        nativeConstructor();    }    public native void save();    public native void restore();    public native void translate(float x, float y, float z);    public native void rotateX(float deg);    public native void rotateY(float deg);    public native void rotateZ(float deg);    public void getMatrix(Matrix matrix) {        nativeGetMatrix(matrix.native_instance);    }    public void applyToCanvas(Canvas canvas) {        nativeApplyToCanvas(canvas.mNativeCanvas);    }    public native float dotWithNormal(float dx, float dy, float dz);        protected void finalize() throws Throwable {        nativeDestructor();    }    private native void nativeConstructor();    private native void nativeDestructor();    private native void nativeGetMatrix(int native_matrix);    private native void nativeApplyToCanvas(int native_canvas);        int native_instance;}