sql - Java - SQLite Database is locked when dropping table -

i trying delete column in sqlite database table using jdbc. there no such function in sqlite, achieve this, used approach:

1. create new table (t1_backup) columns not 1 deleted,
2. copy data (except of column deleted) new table,
3. drop old table (t1),
4. rename new table (t1_backup --> t1).

the actual code follows:

connection cn = drivermanager.getconnection("jdbc:sqlite:"+path); statement stmt = new statement(); stmt = cn.createconnection(); stmt.execute("create table t1_backup(id);"); stmt.executeupdate("insert t1_backup select id t1;"); stmt.execute("drop table t1;"); stmt.execute("alter table t1_backup rename t1;"); 

the first 2 statements executed without problem. when drop table statement executed, gave me java.sql.sqlexception: [sqlite_locked] table in database locked (database table locked).

i have found solution not sure why worked. solution create 3 more statement objects, connect them same database , execute each of 4 sql statements different statement object:

stmt.execute("create ..."); stmt2.executeupdate("insert ..."); stmt3.execute("drop ..."); stmt4.execute("alter ..."); 

can explained?

the jdbc using 1 xerial.

thank you.