Skip to main content

Guava: Defensive coding with Preconditions class



Basic idea behind Defensive coding is not making any assumptions while writing the code and escalating the problem in it's early stage (known as fail fast technique).

This is very simple and effective technique for securing your code from unseen defects.

Guava provide very useful utility class Preconditions for these type of check.


   public static void salaryHike(User user, float salaryHike){
        Preconditions.checkNotNull(user);
        //assuming user will never demoted :)) 
        Preconditions.checkArgument(salaryHike > 0, "salary hike must be positive"); 
        Preconditions.checkState(Validator.validateUser(user), "User is not valid");
        user.salary = user.salary + salaryHike;
    }


Comments

Popular posts from this blog

ERROR: Ignored call to 'alert()'. The document is sandboxed, and the 'allow-modals' keyword is not set.

Recently I found this issue while writing code snippet in "JSFiddle". And after searching, found this was happening because of new feature added in "Chrome 46+". But at the same time Chrome doesn't have support for "allow-modals" property in "sandbox" attribute.

Chromium issue for above behavior:
https://codereview.chromium.org/1126253007

To make it work you have to add "allow-scripts allow-modals" in "sandbox" attribute, and use "window.alert" instead of "alert".



<!-- Sandbox frame will execute javascript and show modal dialogs --> <iframe sandbox="allow-scripts allow-modals" src="iframe.html"> </iframe>


Feature added: Block modal dialog inside a sandboxed iframe.
Link: https://www.chromestatus.com/feature/4747009953103872

Feature working Demo page:
https://googlechrome.github.io/samples/block-modal-dialogs-sandboxed-iframe/index.html



CSS Specificity

Many time different CSS rules overlap on one or more element. And some people always get confuse about, which rule will take higher priority then other and why? CSS Specificity is the answer of all these kind of questions.
As the name suggest, the CSS rule which is more specific to the element will take higher priority then other. Means something like “#some_id{}” will always take higher priority then “*{}” universal selector.  And if duplicate rules are define then the last rule will be applied to the element.

The following list of selectors is by increasing specificity:
Type selector (e.g., div) and pseudo-elements in selector (e.g., :after) Class selectors (e.g., .some_class), attributes selectors (e.g., [type=”radio”]) and pseudo-class selector (e.g., :hover) Id selectors (e.g., #some_id)


ID takes higher priority then Class, Type and Universal selector (Note: Universal selector has no effect on specificity, see below special conditions). 



If duplicate rules are given, then last…

JavaScript [ExtJs3]: EditorGridPanel Read-Only (dynamically)

Many time we face the scenerio where we have to make the editor grid read-only dynamically.


Ext.override(Ext.ux.grid.CheckColumn, { editable: true, onMouseDown: function (e, t) { if (Ext.fly(t).hasClass(this.createId())) { e.stopEvent(); var me = this, grid = me.grid, view = grid.getView(), index = view.findRowIndex(t), colindex = view.findCellIndex(t), record = grid.store.getAt(index); if (!grid.isReadOnly && grid.colModel.isCellEditable(colindex, index)) { record.set(me.dataIndex, !record.data[me.dataIndex]); } } } }); var grid = new Ext.grid.EditorGridPanel({ ... isReadOnly: true, //set to flag to make check column readonly ... }); //to make other column readonly grid.on('beforeedit', function () { return false; });