Java Enum get value from String

Problem:

In Java, I have an Enum and I'd like to be able to look up one of its value using a String.

Solution:

In order to get a specific Enum value from a String, use the java.lang.Enum.valueOf() function.

For instance, if I have the following Enum:

enum Day {Mo, Tu, We, Th, Fr, Sa, Su}

Then the following code gets Day.Th from the String "Th":

Day.valueOf("Th")

Another example, assuming the above Enum Day is defined:

Day myDayExample;
myDayExample = Day.valueOf("Th");

System.out.println(myDayExample); // prints: Th

Notes:

If either the Enum type or string is null, then java.lang.Enum.valueOf() will throw a NullPointerException.

Additionally, if no Enum constant with the name in the String exists, an IllegalArgumentException will be thrown.

For more information, check out the references below.

References:

• https://www.tutorialspoint.com/java/lang/enum_valueof.htm
• http://stackoverflow.com/questions/604424/lookup-enum-by-string-value
• https://docs.oracle.com/javase/7/docs/api/java/lang/Enum.html

Efficient way to find the sign of a number in Java

Problem:

What is an efficient way to find the sign of a number in Java?

Solution:

To find the sign of a number, you can use the signum() function. (e.g. Math.signum(), Integer.signum(), Long.signum(), etc.)

For example:

int sign1 = (int) Math.signum(-123); // -1
int sign2 = (int) Math.signum(222);  //  1
int sign3 = Integer.signum(-1234);   // -1

double sign4 = Math.signum(-123.0);  // -1.0
float sign5 = Math.signum(111.0f);   //  1.0f

double sign6 = Math.signum(0.0);     //  0.0

Notes:

For more information (minimum JDK version, etc.), check out the references below.

References:

• https://docs.oracle.com/javase/7/docs/api/java/lang/Math.html
• http://www.java2novice.com/java-fundamentals/math/signum/
• http://stackoverflow.com/questions/13988805/fastest-way-to-get-sign-in-java

Javascript Unix time to UTC string in Chrome console

Problem:

In the Chrome Dev Tools console, I'd like to view a Unix Time numerical value/timestamp as a human-readable UTC date/time string.

Solution:

In the Chrome Dev Tools console (and in general), one way to view a Unix (POSIX/Epoch) Time as a human-readable UTC string is to use Javascript Date.

For example, if the number of seconds since Epoch is 1480528272, we can convert this in the console by:

new Date(1480528272*1000).toUTCString()

Note that we need to convert the number of seconds to milliseconds since Epoch by multiplying by 1000.

Notes:

Note that due to the size of a Javascript integer, overflow may occur if the desired timestamp is larger than Number.MAX_SAFE_INTEGER.

A Javascript Date object also has a valid range that must be adhered to. More information can be found in here.

References:

• http://www.w3schools.com/jsref/jsref_obj_date.asp
• https://developer.mozilla.org/en/docs/Web/JavaScript/Reference/Global_Objects/Date
• https://developer.mozilla.org/en/docs/Web/JavaScript/Reference/Global_Objects/Number/MAX_SAFE_INTEGER

GWT disable CellTable row highlight on mouse hover

Problem:

In GWT 2.7, how do I disable CellTable row highlight during mouse hover?

Solution:

Imagine your CellTable is named theTable. To disable the mouse-hover row highlighting, try the following:

theTable.setSkipRowHoverStyleUpdate(true);

Notes:

This was verified to work in GWT 2.7. Your mileage may vary with other versions. This reminder was meant as a quick reference for myself, so it's a bit brief. Check out the references below for more detail.

Also note that the above code might also work for GXT DataGrid, depending on version.

References:

• http://www.gwtproject.org/javadoc/latest/com/google/gwt/user/cellview/client/CellTable.html
• http://stackoverflow.com/questions/13138148/gwt-datagrid-disable-mouse-hover-selection
• https://docs.sencha.com/gxt/5.x/javadoc/gwt-2.8.0/gwt-2.8.0/com/google/gwt/user/cellview/client/DataGrid.html

Convert C# bytes to human-readable strings

Problem:

How do I convert a C# byte into a string so that I can read all 8 digits?

Solution:

Imagine that you have a C# byte named myByte. To get a string containing all 8 binary digits, you can use the following code:

  Convert.ToString(myByte, 2).PadLeft(8, '0');

Notes:

Also remember that the Convert.ToString method is in the System namespace.

References:

https://msdn.microsoft.com/en-us/library/system.convert.tostring(v=vs.110).aspx https://msdn.microsoft.com/en-us/library/system.string.padleft(v=vs.110).aspx http://stackoverflow.com/questions/4829366/byte-to-binary-string-c-sharp-display-all-8-digits

C# selectively disable warnings

Problem:

I would like to selectively disable C# warnings.

Solution:

The syntax to selectively disable warnings is:

#pragma warning disable <warning number or warning list>
   <code block where warning is to be ignored>
#pragma warning restore <warning number or warning list>

Example:

#pragma warning disable 0618
  MyNecessaryObsoleteFunctionCall();
#pragma warning restore 0618

BadObsoleteCallThatShouldProduceWarning();

Notes:

C# compiler warnings are generally there for good reason, so it's better practice to resolve them rather than hide them. However, in some situations willfully ignoring/acknowledging a warning might be necessary (e.g. if warnings block your team's build, but the code is temporarily required for some important reason).

References:

https://msdn.microsoft.com/en-ca/library/441722ys.aspx http://stackoverflow.com/questions/968293/c-sharp-selectively-suppress-custom-obsolete-warnings

View GWT emulated Long in browser developer tools

Problem:

I would like to see the long value of a GWT emulated Long in my browser's developer tools.

I already know how to pause and debug my web app, but when I inspect a Long value, it looks similar to {h:0, m:544, l:54210}.

Solution:

Imagine that we have an emulated Long value: myLongVal={h:1, m:234, l:567}

To translate this to a human-readable Long (in most, but not all cases), type the following in the developer tools console:

myLongVal.h*Math.pow(2,44) + myLongVal.m*Math.pow(2,22) + myLongVal.l

(See screenshot)

Notes:

This was verified to work in GWT 2.7. Your mileage may vary for other versions.

The above method should work for Long values that are low enough. However, overflow may occur for larger emulated Long values as the cast to a Javascript double does not cover as many bits as a long integer.

Note that if you have a browser that actually supports 64-bit integers or larger, you might be able to use the following:

(myLongVal.h << 44) + (myLongVal.m << 22) + myLongVal.l

References:

• https://github.com/gwtproject/gwt/blob/master/dev/core/super/com/google/gwt/lang/BigLongLibBase.java

Chrome CPU throttling

Problem:

I would like to slow down, or throttle Chrome to test my web app's responsiveness. My computer is too fast to represent devices in the real world.

Solution:

Enable CPU throttling in Chrome Developer Tools:

• F12 to open developer tools in Chrome
• click on the "Timeline" tab
• click the CPU throttling drop-down (beside the trash can/garbage collect icon) (see image below)
• select your desired throttle speed

Notes:

This was verified to work in Chrome version 54. Your mileage my vary with different versions and on different machines.

Also note that while this may help simulate and uncover some performance issues for scripts during development, it may not completely simulate issues experienced on slower devices. Using a virtual machine, or a real test machine would generally be preferred for more comprehensive testing.

Nonetheless, a big "thank you" to the Chrome developers for including such a useful feature :)

References:

• https://plus.google.com/+AddyOsmani/posts/NRsAqshb17n

Package-level javadoc comments

Problem:

How can I add package-level javadoc comments to my Java project?

Solution:

• In your package's directory, add a file named "package-info.java"
• In this file, include the package-level javadoc comment, as well as the package declaration

Example:

myprojectroot/mypackage/package-info.java:

/**
 * Provides an example package-level javadoc comment.
 * 
 * @since 1.0
 */
package myprojectroot.mypackage;

Additional hints:

• in Eclipse, you can create this file by adding a "new file" to the package (instead of a new Java class, etc.)

References:

• http://docs.oracle.com/javase/1.5.0/docs/tooldocs/windows/javadoc.html#packagecomment
• http://stackoverflow.com/questions/3650907/how-to-add-package-level-comments-in-javadoc

Copy local scope variables in Chrome developer tools

Problem:

I would like to use Chrome developer tools to access local scoped variables when debugging Javascript applications.

I am already familiar with debugging with using developer tools, including setting breakpoints and pausing code execution.

How to reminder:

• set break point to pause execution within the desired scope
• to access the local scope variable, type it in the console while script execution is still paused in the desired scope (see image below)

Notes:

This was verified to work in Chrome version 54. Your mileage may vary using other versions.

Clear icon cache in windows 7/8/10

Problem:

I want to clear the Windows icon cache because a Windows shortcut is currently displaying an old, incorrect icon.

Solution:

• press [Windows Key]+R (to get the run dialog)
• in windows 7/8, run the command: ie4uinit.exe -ClearIconCache
• in windows 10, run the command: ie4uinit.exe -show

Additional notes:

This was verified to work in Windows 7 and Windows 10 without requiring a restart. Your mileage may vary.

References:

• http://www.winhelponline.com/blog/refresh-icon-cache-windows-7-quickly/
• http://superuser.com/questions/499078/refresh-icon-cache-without-rebooting