The second option is well explored in research and some existing tools like the Checker Framework, JML, FindBugs already introduce specific annotations to this end. One could argue that advanced analysis should be left to specialized tools but having something like this in the JDT compiler should show two benefits:.
By default the JDT does not support inter-procedural null analysis, however, starting with 3. Up-to-date documentation for the annotation-based null analysis and its new configuration options can be found in the Eclipse help Eclipse 3. Null annotations in method signatures can be interpreted as null contracts , however, a more general approach considers null annotations as an extension of the type system.
Since the availability of JSR all type references should either include or exclude null, which allows for complete checking of any possible dereferencing of null. In other words, a fully annotated program which passes the type checker will never raise an NPE at runtime. To achieve this guarantee two annotations are used. The specific annotations types can be selected as a preference, but the following defaults are provided:. For any variable who's type is annotated with NonNull or the configured equivalent the following rules apply:.
For any variable who's type is annotated with Nullable or the configured equivalent the following rules apply:. The above rules imply that the value from a NonNull variable can be bound to a variable annotated with Nullable, but the opposite direction is generally illegal.
Only after an explicit null check can a Nullable variable be treated as being NonNull for the sake of binding to another NonNull variable or for dereferencing. For fields the situation is actually more complex — please read "The case of fields". For interaction with inheritance see Null Contract Inheritance. In order to try the new analysis against any existing Java project the following steps should help:. When applying the new analysis to a big existing project, the sheer number of new problems may look intimidating but that's where quick fixes will come to the rescue.
Currently the following problems offer a quickfix:. Note, that some quick fixes require to modify another compilation unit file than the one where the problem was observed.
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Related Hot Network Questions. Question feed. Stack Overflow works best with JavaScript enabled. Accept all cookies Customize settings. Indexing is zero based. The range of a selection is from N where N is the number of characters in the widget. If the text field is editable, this has the effect of placing the i-beam at the start of the text.
Note: To clear the selected items in the receiver's list, use deselectAll. Parameters: string - the new item Throws: java.
Note: To add an item at the end of the list, use the result of calling getItemCount as the index or use add String. Parameters: string - the new item index - the index for the item Throws: java. Parameters: index - the index for the item Throws: java.
Parameters: start - the start of the range end - the end of the range Throws: java. Parameters: string - the item to remove Throws: java. This is equivalent to removing the old item at the index, and then adding the new item at that index.
Parameters: index - the index for the item string - the new text for the item Throws: java. Parameters: items - the array of items Throws: java. Throws an exception if the index is out of range. Parameters: index - the index of the item to return Returns: the item at the given index Throws: java.
Note: This is not the actual structure used by the receiver to maintain its list of items, so modifying the array will not affect the receiver. Note: This operation is a hint and is not supported on platforms that do not have this concept. If one of the receiver's ancestors is not visible or some other condition makes the receiver not visible, marking it visible may not actually cause it to be displayed.
If one of the receiver's ancestors is not visible or some other condition makes the receiver not visible, this method may still indicate that it is considered visible even though it may not actually be showing. If no item is found, returns Parameters: string - the search item Returns: the index of the item Throws: java.
If no item is found or the starting index is out of range, returns Parameters: string - the search item start - the zero-relative index at which to begin the search Returns: the index of the item Throws: java. Note: The text field in a Combo is typically only capable of displaying a single line of text. Thus, setting the text to a string containing line breaks or other special characters will probably cause it to display incorrectly.
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