我在ubuntu16.04上使用java-1.8.0-openjdk-amd64
我试图理解在附加时文件会发生什么
假设我附加到一个非常大的文件，java是否将整个文件加载到内存中？如何查看本机呼叫？
从java.io.fileoutputstream.java

/**
 * Opens a file, with the specified name, for overwriting or appending.
 * @param name name of file to be opened
 * @param append whether the file is to be opened in append mode
 */
private native void open0(String name, boolean append)
    throws FileNotFoundException;

// wrap native call to allow instrumentation
/**
 * Opens a file, with the specified name, for overwriting or appending.
 * @param name name of file to be opened
 * @param append whether the file is to be opened in append mode
 */
private void open(String name, boolean append)
    throws FileNotFoundException {
    open0(name, append);
}

更新：
查看jdk8源代码
src/solaris/native/sun/nio/ch/inheritedchannel.c:java\u sun\u nio\u ch\u inheritedchannel\u open0（jnienv*env，jclass cla，jstring path，jint of lag）

JNIEXPORT jint JNICALL
Java_sun_nio_ch_InheritedChannel_open0(JNIEnv *env, jclass cla, jstring path, jint oflag)
{
    const char* str;
    int oflag_actual;

    /* convert to OS specific value */
    switch (oflag) {
        case sun_nio_ch_InheritedChannel_O_RDWR :
            oflag_actual = O_RDWR;
            break;
        case sun_nio_ch_InheritedChannel_O_RDONLY :
            oflag_actual = O_RDONLY;
            break;
        case sun_nio_ch_InheritedChannel_O_WRONLY :
            oflag_actual = O_WRONLY;
            break;
        default :
            JNU_ThrowInternalError(env, "Unrecognized file mode");
            return -1;
    }

    str = JNU_GetStringPlatformChars(env, path, NULL);
    if (str == NULL) {
        return (jint)-1;
    } else {
        int fd = open(str, oflag_actual);
        if (fd < 0) {
            JNU_ThrowIOExceptionWithLastError(env, str);
        }
        JNU_ReleaseStringPlatformChars(env, path, str);
        return (jint)fd;
    }
}