public class Test { public static void main(String[] args) { int stop = 4; for(int i = 1; i <= 6; i++) { if(i == stop) break; System.out.println("i = " + i); } } }这个代码的结果是什么

这段代码的输出结果是：

i = 1
i = 2
i = 3

这是因为在 for 循环中，变量 i 的初始值是 1，每次循环 i 自增 1，直到 i 大于 6 时，循环结束。

在每次循环中，我们使用 if 语句判断 i 是否等于 stop，当 i 等于 4 时，使用 break 语句跳出循环。因此，当 i 等于 4 时，循环被终止，后面的语句不再执行，所以只输出了三个 i 的值。

相关问题

android中 MediaCodec 压缩视频使用示例,带调用的main方法，压缩一个测试的视频

好的，以下是一个简单的使用 MediaCodec 压缩视频的示例代码，包括调用的 main 方法和压缩测试视频：

import android.media.MediaCodec;
import android.media.MediaCodecInfo;
import android.media.MediaFormat;
import android.media.MediaMuxer;
import android.os.Environment;
import android.util.Log;

import java.io.File;
import java.io.FileInputStream;
import java.io.IOException;
import java.nio.ByteBuffer;

public class VideoCompressor {

    private static final String TAG = "VideoCompressor";
    private static final String TEST_VIDEO_PATH = Environment.getExternalStorageDirectory() + "/test.mp4";
    private static final String COMPRESSED_VIDEO_PATH = Environment.getExternalStorageDirectory() + "/compressed.mp4";
    private static final String MIME_TYPE = "video/avc";
    private static final int FRAME_RATE = 30;
    private static final int I_FRAME_INTERVAL = 1;
    private static final int BIT_RATE = 500000;

    public static void main(String[] args) {
        try {
            VideoCompressor compressor = new VideoCompressor();
            compressor.compressVideo(TEST_VIDEO_PATH, COMPRESSED_VIDEO_PATH);
        } catch (Exception e) {
            e.printStackTrace();
        }
    }

    public void compressVideo(String inputFilePath, String outputFilePath) throws IOException {
        Log.i(TAG, "compressVideo: inputFilePath=" + inputFilePath + ", outputFilePath=" + outputFilePath);

        // Read input video file
        FileInputStream inputFile = new FileInputStream(new File(inputFilePath));
        byte[] inputData = new byte[inputFile.available()];
        inputFile.read(inputData);
        inputFile.close();

        // Set up MediaCodec encoder
        MediaCodec encoder = MediaCodec.createEncoderByType(MIME_TYPE);
        MediaFormat format = MediaFormat.createVideoFormat(MIME_TYPE, 1920, 1080);
        format.setInteger(MediaFormat.KEY_COLOR_FORMAT, MediaCodecInfo.CodecCapabilities.COLOR_FormatSurface);
        format.setInteger(MediaFormat.KEY_BIT_RATE, BIT_RATE);
        format.setInteger(MediaFormat.KEY_FRAME_RATE, FRAME_RATE);
        format.setInteger(MediaFormat.KEY_I_FRAME_INTERVAL, I_FRAME_INTERVAL);
        encoder.configure(format, null, null, MediaCodec.CONFIGURE_FLAG_ENCODE);
        encoder.start();

        // Set up MediaMuxer
        MediaMuxer muxer = new MediaMuxer(outputFilePath, MediaMuxer.OutputFormat.MUXER_OUTPUT_MPEG_4);

        // Start encoding
        ByteBuffer[] inputBuffers = encoder.getInputBuffers();
        ByteBuffer[] outputBuffers = encoder.getOutputBuffers();
        MediaCodec.BufferInfo bufferInfo = new MediaCodec.BufferInfo();
        boolean isInputDone = false;
        boolean isOutputDone = false;
        int frameCount = 0;
        while (!isOutputDone) {
            if (!isInputDone) {
                int inputBufferIndex = encoder.dequeueInputBuffer(-1);
                if (inputBufferIndex >= 0) {
                    ByteBuffer inputBuffer = inputBuffers[inputBufferIndex];
                    inputBuffer.clear();
                    inputBuffer.put(inputData);
                    encoder.queueInputBuffer(inputBufferIndex, 0, inputData.length, frameCount * 1000000 / FRAME_RATE, 0);
                    frameCount++;
                } else {
                    isInputDone = true;
                }
            }

            while (!isOutputDone) {
                int outputBufferIndex = encoder.dequeueOutputBuffer(bufferInfo, 0);
                if (outputBufferIndex == MediaCodec.INFO_TRY_AGAIN_LATER) {
                    break;
                } else if (outputBufferIndex == MediaCodec.INFO_OUTPUT_FORMAT_CHANGED) {
                    MediaFormat newFormat = encoder.getOutputFormat();
                    Log.i(TAG, "compressVideo: output format changed: " + newFormat);
                    muxer.addTrack(newFormat);
                } else if (outputBufferIndex < 0) {
                    Log.w(TAG, "compressVideo: unexpected result from encoder.dequeueOutputBuffer: " + outputBufferIndex);
                } else {
                    ByteBuffer outputBuffer = outputBuffers[outputBufferIndex];
                    if ((bufferInfo.flags & MediaCodec.BUFFER_FLAG_CODEC_CONFIG) != 0) {
                        bufferInfo.size = 0;
                    }

                    if (bufferInfo.size != 0) {
                        outputBuffer.position(bufferInfo.offset);
                        outputBuffer.limit(bufferInfo.offset + bufferInfo.size);
                        muxer.writeSampleData(0, outputBuffer, bufferInfo);
                    }

                    encoder.releaseOutputBuffer(outputBufferIndex, false);

                    if ((bufferInfo.flags & MediaCodec.BUFFER_FLAG_END_OF_STREAM) != 0) {
                        isOutputDone = true;
                    }

                    break;
                }
            }
        }

        // Release resources
        muxer.stop();
        muxer.release();
        encoder.stop();
        encoder.release();

        Log.i(TAG, "compressVideo: done");
    }
}

这个示例代码会读取指定路径下的 `test.mp4` 视频文件，并使用 MediaCodec 将其压缩为指定路径下的 `compressed.mp4` 文件。压缩的视频编码格式为 H.264，分辨率为 1920x1080，帧率为 30 帧/秒，关键帧间隔为 1 秒，比特率为 500000 bps。这些参数可以根据实际需要进行修改。

mariadb4j java代码

以下是使用 MariaDB4j 的 Java 代码示例：

import ch.vorburger.mariadb4j.DB;
import ch.vorburger.mariadb4j.DBConfigurationBuilder;
import ch.vorburger.mariadb4j.springframework.MariaDB4jSpringService;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;

import javax.sql.DataSource;
import java.sql.Connection;
import java.sql.PreparedStatement;
import java.sql.ResultSet;
import java.sql.SQLException;

@Configuration
public class MariaDB4jConfig {

    @Bean
    public MariaDB4jSpringService mariaDB4jSpringService() throws Exception {
        DBConfigurationBuilder config = DBConfigurationBuilder.newBuilder();
        config.setPort(3307); // 设置端口号
        config.setDataDir("target/mariadb4j/data"); // 设置数据目录
        config.setBaseDir("target/mariadb4j"); // 设置 MariaDB 基础目录

        DB db = DB.newEmbeddedDB(config.build());
        db.start();

        // 创建测试表格
        Connection conn = db.getConnection();
        PreparedStatement ps = conn.prepareStatement("CREATE TABLE IF NOT EXISTS test (id INT PRIMARY KEY, name VARCHAR(255))");
        ps.execute();
        ps.close();
        conn.close();

        return new MariaDB4jSpringService(db);
    }

    @Bean
    public DataSource dataSource(MariaDB4jSpringService mariaDB4jSpringService) throws SQLException {
        return mariaDB4jSpringService.getDataSource();
    }

    // 测试代码
    public static void main(String[] args) throws Exception {
        MariaDB4jSpringService mariaDB4jSpringService = new MariaDB4jConfig().mariaDB4jSpringService();
        DataSource dataSource = mariaDB4jSpringService.getDataSource();

        Connection conn = dataSource.getConnection();
        PreparedStatement ps = conn.prepareStatement("INSERT INTO test (id, name) VALUES (?, ?)");
        ps.setInt(1, 1);
        ps.setString(2, "Test");
        ps.execute();
        ps.close();

        ps = conn.prepareStatement("SELECT * FROM test");
        ResultSet rs = ps.executeQuery();
        while (rs.next()) {
            System.out.println(rs.getInt("id") + " " + rs.getString("name"));
        }
        ps.close();
        conn.close();

        mariaDB4jSpringService.getDB().stop();
    }
}

这个示例代码创建了一个 MariaDB4jSpringService 实例，并在其中创建了一个测试表格。然后它使用创建的 MariaDB4jSpringService 实例连接到数据库，插入一条记录并读取记录。最后，它停止了 MariaDB 数据库。