android java program yardım !

[armsistem]

Arkadaşlar merhaba ;  aşağıdaki programı inceliyorum fakat anlayamadığım bir nokta var

public class UsbRequest {

  // arkadaş burada değişkenleri vermiş vermiş eyvallah

    public UsbRequest() {
// peki neden böyle bir şey yapıyor olerloading dediklerimi
    }


Tam Kod

/*
 * Copyright (C) 2010 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.hardware.usb;

import android.util.Log;

import java.nio.ByteBuffer;

/**
 * A class representing USB request packet.
 * This can be used for both reading and writing data to or from a
 * {@link android.hardware.usb.UsbDeviceConnection}.
 * UsbRequests can be used to transfer data on bulk and interrupt endpoints.
 * Requests on bulk endpoints can be sent synchronously via {@link UsbDeviceConnection#bulkTransfer}
 * or asynchronously via {@link #queue} and {@link UsbDeviceConnection#requestWait}.
 * Requests on interrupt endpoints are only send and received asynchronously.
 *
 * <p>Requests on endpoint zero are not supported by this class;
 * use {@link UsbDeviceConnection#controlTransfer} for endpoint zero requests instead.
 */
public class UsbRequest {

    private static final String TAG = "UsbRequest";

    // used by the JNI code
    private int mNativeContext;

    private UsbEndpoint mEndpoint;

    // for temporarily saving current buffer across queue and dequeue
    private ByteBuffer mBuffer;
    private int mLength;

    // for client use
    private Object mClientData;

    public UsbRequest() {
    }

    /**
     * Initializes the request so it can read or write data on the given endpoint.
     * Whether the request allows reading or writing depends on the direction of the endpoint.
     *
     * @param endpoint the endpoint to be used for this request.
     * @return true if the request was successfully opened.
     */
    public boolean initialize(UsbDeviceConnection connection, UsbEndpoint endpoint) {
        mEndpoint = endpoint;
        return native_init(connection, endpoint.getAddress(), endpoint.getAttributes(),
                endpoint.getMaxPacketSize(), endpoint.getInterval());
    }

    /**
     * Releases all resources related to this request.
     */
    public void close() {
        mEndpoint = null;
        native_close();
    }

    @Override
    protected void finalize() throws Throwable {
        try {
            if (mEndpoint != null) {
                Log.v(TAG, "endpoint still open in finalize(): " + this);
                close();
            }
        } finally {
            super.finalize();
        }
    }

    /**
     * Returns the endpoint for the request, or null if the request is not opened.
     *
     * @return the request's endpoint
     */
    public UsbEndpoint getEndpoint() {
        return mEndpoint;
    }

    /**
     * Returns the client data for the request.
     * This can be used in conjunction with {@link #setClientData}
     * to associate another object with this request, which can be useful for
     * maintaining state between calls to {@link #queue} and
     * {@link android.hardware.usb.UsbDeviceConnection#requestWait}
     *
     * @return the client data for the request
     */
    public Object getClientData() {
        return mClientData;
    }

    /**
     * Sets the client data for the request.
     * This can be used in conjunction with {@link #getClientData}
     * to associate another object with this request, which can be useful for
     * maintaining state between calls to {@link #queue} and
     * {@link android.hardware.usb.UsbDeviceConnection#requestWait}
     *
     * @param data the client data for the request
     */
    public void setClientData(Object data) {
        mClientData = data;
    }

    /**
     * Queues the request to send or receive data on its endpoint.
     * For OUT endpoints, the given buffer data will be sent on the endpoint.
     * For IN endpoints, the endpoint will attempt to read the given number of bytes
     * into the specified buffer.
     * If the queueing operation is successful, we return true and the result will be
     * returned via {@link android.hardware.usb.UsbDeviceConnection#requestWait}
     *
     * @param buffer the buffer containing the bytes to write, or location to store
     * the results of a read
     * @param length number of bytes to read or write
     * @return true if the queueing operation succeeded
     */
    public boolean queue(ByteBuffer buffer, int length) {
        boolean out = (mEndpoint.getDirection() == UsbConstants.USB_DIR_OUT);
        boolean result;
        if (buffer.isDirect()) {
            result = native_queue_direct(buffer, length, out);
        } else if (buffer.hasArray()) {
            result = native_queue_array(buffer.array(), length, out);
        } else {
            throw new IllegalArgumentException("buffer is not direct and has no array");
        }
        if (result) {
            // save our buffer for when the request has completed
            mBuffer = buffer;
            mLength = length;
        }
        return result;
    }

    /* package */ void dequeue() {
        boolean out = (mEndpoint.getDirection() == UsbConstants.USB_DIR_OUT);
        if (mBuffer.isDirect()) {
            native_dequeue_direct();
        } else {
            native_dequeue_array(mBuffer.array(), mLength, out);
        }
        mBuffer = null;
        mLength = 0;
    }

    /**
     * Cancels a pending queue operation.
     *
     * @return true if cancelling succeeded
     */
    public boolean cancel() {
        return native_cancel();
    }

    private native boolean native_init(UsbDeviceConnection connection, int ep_address,
            int ep_attributes, int ep_max_packet_size, int ep_interval);
    private native void native_close();
    private native boolean native_queue_array(byte[] buffer, int length, boolean out);
    private native void native_dequeue_array(byte[] buffer, int length, boolean out);
    private native boolean native_queue_direct(ByteBuffer buffer, int length, boolean out);
    private native void native_dequeue_direct();
    private native boolean native_cancel();
}

[Tagli]

Android programlamayı bilmiyorum ama o bahsettiğin özel bir fonksiyon ve constructor olarak anılır. Nesne ilk oluşturulurken otomatik olarak çağrılır ve başlangıçta yapılması gereken şeyleri yapar. Eğer kodda hiç constructor yazılmamışsa derleyici kendisi otomatik olarak boş bir tane oluşturur. Yani verdiğin kodda o kısım olmasa da olurmuş sanırım. Çünkü zaten boş bırakmış.

[armsistem]

aynen, bende java da yeniyim ama bildiğim dillerle mantık kurmayı denedim olmadı acaba javaya özgümüdür dedim.

[Tagli]

Constructor mantığı Java'ya özgü değil ama her dilde özellikleri aynı olmayabiliyor. Örneğin Java'da bir constructor aynı sınıf içindeki overload edilmiş bir başka constructor'ı çağırabilir (buna constructor chaining denir) ama C++ buna izin vermez. Python'da ise constructor yoktur ama benzer işi yapan __init__ diye bir fonksiyon bulunur.