question: public SQLiteTableBuilder addColumn ( String columnName , int type , boolean primaryKey ) { if ( TextUtils . isEmpty ( columnName ) ) { throw new IllegalArgumentException ( "Column name cannot be empty." ) ; } else if ( ! columnName . matches ( REGEX_SQL_IDENTIFIER ) ) { throw new IllegalArgumentException ( "Invalid column name." ) ; } if ( mHasColumns ) { mStringBuilder . append ( COMMA ) ; } mStringBuilder . append ( columnName ) ; appendType ( type ) ; if ( primaryKey ) { mStringBuilder . append ( PRIMARY_KEY ) ; } mHasColumns = true ; return this ; }
target:  Adds a column to the current table.