Java Solutions: August 2017

Wednesday, August 23, 2017

Turn off the pop up notification at the bottom right corner of the screen

While you are using the Chrome browser, it is annoying to have one or multiple pop-up notifications showing at the bottom-right corner of the screen.

To turn the notification off:

Click the up arrow icon or the vertical three dots icon on the right of the top URL input and select Settings.
Go the bottom of the Settings list to open the Advanced.
Click on Content Settings
Click on Notifications
Click on the sliding ball at the right end of the first line to let it slide to the left and Blocked replaces the words "Ask before sending (recommended)" at the left end of the first line.

To turn off pop-ups

Click the up arrow icon on the right of the top URL input and select Settings.
Go the bottom of the Settings list to open the Advanced.
Click on Content Settings
Click on Popups
Click on the sliding ball at the right end of the first line to let it slide to the left and "Blocked (recommended)" replaces the word "Allowed" at the left end of the first line.

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Tuesday, August 22, 2017

[Solved] Spreadsheet: Write multiple lines in one cell for LibreOffice, WPS Spreadsheets, and Office

LibreOffice:

Make a list of texts in a cell: While the text entering cursor is in the cell, hold down the Ctrl key and click the Enter key. This will break the current line at the text entering cursor and start a new line. This also works when the cursor is in the top input line. The top input line can be expanded to multiple lines by pressing the down arrow button on the right of the input line.
Wrap text so that it fits into the boundary of a cell: Click in the cell, click on the Format in the top ribbon manual and select Cells. In the popped up window, select the Alignment tab and check the Wrap text automatically checkbox.

WPS Spreadsheets:

1. Make a list of texts in a cell: Double click on the cell, click to insert the text input cursor to the location where you want to break the line, hold down the Alt key and click the Enter key to make a new line.

2. Wrap text so that it fits into the boundary of a cell: Select the cell, and then click the Wrap Text icon in the top ribbon menu on the Home tab.

Office Excel:

Make a list of texts in a cell: Double click on the cell, click to insert the text input cursor to the location where you want to break the line, hold down the Alt key and click the Enter key to make a new line.
Wrap text so that it fits into the boundary of a cell: Select the cell or range you want to wrap text, click the Wrap Text in the Alignment group on the Home tab in the top ribbon manual.

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Thursday, August 17, 2017

Crystalreports ERROR JRCCommunicationAdapter - detected an exception: java.lang.NullPointerException

The Crystal report displays this popped up the message first.

It then shows this popped up message.

In the console, it prints:

ERROR JRCCommunicationAdapter - detected an exception: Unexpected database connector error
at com.crystaldecisions.reports.datafoundation.DFQuery.for(SourceFile:632)
at com.crystaldecisions.reports.datalayer.a.do(SourceFile:1621)

. . . . . .

Unexpected database connector error
ERROR JRCCommunicationAdapter - detected an exception: java.lang.NullPointerException
at com.crystaldecisions.reports.dataengine.DataContext.try(SourceFile:734)
at com.crystaldecisions.reports.dataengine.DataProcessor2.u(SourceFile:1257)

. . . . . .

java.lang.NullPointerException

One of the causes of this error is that the SQL does not have all the tables needed in the FROM clause or the JOIN clauses. For example, the following situation will incur such an error.

The SQL of the reprot:

SELECT employee.name, sales.quantity
FROM employee
INNER JOIN sales on employee.id = sales.empid
where sales.quantity > 100 and {?whereClause}

The whereClause is set to:

product.name='Organic Avacado'

Since the product table is not present in the SQL FROM clause or the JOIN clause, it will throw the exceptions described above.

To fix the problem, change the SQL to:

SELECT employee.name, sales.quantity
FROM employee
INNER JOIN sales on employee.id = sales.empid
INNER JOIN product on sales.productid=product.id
where sales.quantity > 100 and {?whereClause}

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Friday, August 11, 2017

SQL: How to tell if an existing index is unique?

A. Oracle

select INDEX_NAME, UNIQUENESS
from dba_indexes
where owner ='<owner>' and INDEX_NAME = '<index name>';

Sample output:

INDEX_NAME UNIQUENES
------------------------------ ---------
EMPLOYEE_KEY_IDX UNIQUE

B. Postgresql

SELECT relname AS INDEX_NAME, indisunique as UNIQUENESS
FROM pg_class, pg_index
WHERE pg_class.oid = pg_index.indexrelid AND relname !~ '^pg_' and relname = '<index name>';

Sample output:

index_name uniqueness
------------------------------------------+------------
employee_license_idx f

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Thursday, August 10, 2017

ORA-01452: cannot CREATE UNIQUE INDEX; duplicate keys found

This error happens when there are duplicate records in your table. For example, you have an EMPLOYEE table,

firstName lastName id title department
---------------- --------------- ---------- ----------- -------------
Eva Young 223 manager HR
Eva Young 223 VP HD
Tom Lee 519 Sales SA

create unique index uniqueemp on employee (firstName, lastName, id);

The above SQL will generate the error:

ORA-01452: cannot CREATE UNIQUE INDEX; duplicate keys found

To fix this problem, you can do one of the followings.

1. Change the id of one of the Eva Young records to something else.
2. Delete one of the Eva Young record.
3. Remove the unique key word in the creating index SQL.

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