表结构：

?

create table test(
    id varchar2(32) primary key,
    name varchar2(32)
);

import java.sql.Connection;
import java.sql.PreparedStatement;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.sql.Statement;
 
public class Test {
 
    /**
     * 使用Statement.RETURN_GENERATED_KEYS 指定返回生成主键
     */
    public static void main(String[] args) {
 
        PreparedStatement pst = null;
        ResultSet rs = null;
        Connection conn = ConnectionManager.getConnection();
        String sql = "insert into test(id,name) values(?,?)";
        try {
            //String generatedColumns[] = { "ID" };  //获得指定ID
            pst = conn.prepareStatement(sql, Statement.RETURN_GENERATED_KEYS); // 指定返回生成的主键
            pst.setString(1, "123x");
            pst.setString(2, "test");
            int ii = pst.executeUpdate();
 
            // 检索对象生成的键
            rs = pst.getGeneratedKeys();
            if (rs.next()) {
                System.out.println("数据主键：" + rs.getString(1));
            }
            ConnectionManager.closeAll(rs, pst, conn); // 关闭资源
 
        } catch (SQLException e) {
            e.printStackTrace();
        }
    }
}

import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.sql.Statement;
 
public class ConnectionManager {
  public static final String DRIVER = "oracle.jdbc.driver.OracleDriver";
  public static final String URL = "jdbc:oracle:thin:@localhost:1521/orcl";
  public static final String USERNAME = "root";
  public static final String PASSWORD = "root";
  /**
   * 通过静态代码块 注册数据库驱动
   */
  static{
    try {
      Class.forName(DRIVER);
    } catch (ClassNotFoundException e) {
      e.printStackTrace();
    }
  }
 
  /**
   * 获得Connection
   *
   * @return
   */
  public static Connection getConnection() {
    Connection conn = null;
    try {
      conn = DriverManager.getConnection(URL,USERNAME,PASSWORD);
    }catch (SQLException e) {
      e.printStackTrace();
    }
    return conn;
  }
 
  /**
   * 关闭ResultSet
   * @param rs
   */
  public static void closeResultSet(ResultSet rs) {
    if (rs != null) {
      try {
        rs.close();
      } catch (SQLException e) {
        e.printStackTrace();
      }
    }
  }
 
  /**
   * 关闭Statement
   * @param st
   */
  public static void closeStatement(Statement st) {
    if (st != null) {
      try {
        st.close();
      } catch (SQLException e) {
        e.printStackTrace();
      }
    }
  }
 
  /**
   * 关闭Connection
   * @param conn
   */
  public static void closeConnection(Connection conn) {
    if (conn != null) {
      try {
        conn.close();
      } catch (SQLException e) {
        e.printStackTrace();
      }
    }
  }
  /**
   * 关闭全部
   * @param rs
   * @param sta
   * @param conn
   */
  public static void closeAll(ResultSet rs,Statement sta,Connection conn){
    closeConnection(conn);
    closeStatement(sta);
    closeResultSet(rs);
  }
 
}

其实是test表的ROWID字段值

String generatedColumns[] = { "ID" };
pst = conn.prepareStatement(sql, generatedColumns);