在Java中，Apache ORC是一種高效的文件格式，它可以在Hadoop集群中進行分析和查詢。ORC文件格式通常與Apache Hive的數據倉庫一起使用。下面介紹如何使用Java生成和讀取ORC文件。

生成ORC文件

//創建ORC文件寫入器
Configuration conf = new Configuration();
FileSystem fs = FileSystem.get(conf);
Path orcPath = new Path("orc/hive_orc_table.orc");
Writer writer = OrcFile.createWriter(orcPath, OrcFile.writerOptions(conf).setSchema(schema));
// 將數據寫入ORC文件
VectorizedRowBatch batch = schema.createRowBatch();
for (int r = 0; r< rows; ++r) {
int row = batch.size++;
for (int c = 0; c< cols; ++c) {
setVal(c, row, batch.cols[c]);
}
if (batch.size == batch.getMaxSize()) {
writer.addRowBatch(batch);
batch.reset();
}
}
if (batch.size != 0) {
writer.addRowBatch(batch);
batch.reset();
}
writer.close();

讀取ORC文件

Configuration conf = new Configuration();
FileSystem fs = FileSystem.get(conf);
Path orcPath = new Path("orc/hive_orc_table.orc");
Reader reader = OrcFile.createReader(orcPath, OrcFile.readerOptions(conf));
TypeDescription schema = reader.getSchema();
// 讀取ORC文件數據
RecordReader rows = reader.rows();
VectorizedRowBatch batch = schema.createRowBatch();
while (rows.nextBatch(batch)) {
for (int r = 0; r< batch.size; ++r) {
for (int c = 0; c< batch.numCols; ++c) {
Object obj = batch.cols[c].getObject(r);
// 處理數據
}
}
}
rows.close();

以上是Java生成和讀取ORC文件的簡單示例，可以根據實際需求對代碼進行更改和優化。