【单选题】在下面空格中选择填入的数学符号 “= , ≥ , ≤ , >” 或 “<” H(XY) H(Y)+H(X)
【简答题】在下面空格中选择填入的数学符号 “= , ≥ , ≤ , >” 或 “ H(XY) H(Y)+H(X)
【单选题】下列选项中,能够使sqlite数据库的SqliteOpenHelper类自动调用它onUpgrade()方法的操作是( )。
A.
在每次新建DatabaseHelper对象时
B.
用DatabaseHelper调用getReadableDatabase()方法时
C.
在每次调用SqliteDatabase的getWritableDatabase()方法时
D.
当创建DatabaseHelper对象时,数据库版本参数发生变化时
【单选题】在Java Web应用程序中,下列( )选项中的代码能够正确实现使用数据源(DataSource)获取数据库连接对象(数据源名称为dsname)。
A.
DataSource soure = new DataSource( ) ; Connection conn = source.getConnection( );
B.
Context source = new InitalContext( ); Connection conn = source.getConnection( );
C.
Context ctx = new InitalContext( ); DataSource ds = (DataSource) ctx.lookup("java:comp/env/dsname"); Connection conn = ds.getConnection( );
D.
Context ctx = new InitalContext( ); DataSource ds = (DataSource) ctx.lookup("dsname"); Connection conn = ds.getConnection( );
【单选题】According to the text, 'rational choice' holds that
A.
decision making is not linked with wisdom in a sense.
B.
happiness relies on short-term individual gains.
C.
individual happiness harms the broad interests of society.
D.
individual fates change with reckless greed.