First, preface
When coding, we always find a warning that the following variables are not being used:
The code above is compiled and can be run, but the exclamation point in front of each line seriously hinders the breakpoint we have to determine if the line is set. At this point we can add @SuppressWarnings ("unused") before the method to remove these "exclamation marks".
Second, @SuppressWarings annotations
Role: Used to suppress compiler-generated warning messages.
Example to suppress single-type warnings:
@SuppressWarnings ("unchecked") public void Additems (String item) { @SuppressWarnings ("Rawtypes") List items = New ArrayList (); Items.Add (item);}
Example 2--suppresses multiple types of warnings:
@SuppressWarnings (value={"Unchecked", "rawtypes"}) public void Additems (String item) { List items = new ArrayList (); Items.Add (item);}
Example 3--suppresses all types of warnings:
@SuppressWarnings ("all") public void Additems (String item) { List items = new ArrayList (); Items.Add (item);}
Iii. Annotated target
by @SuppressWarnings Source, the annotated target is a local variable of class, field, function, function parameter, constructor and function.
The home recommendation note should be declared at the location closest to where the warning occurred.
Iv. keywords to suppress warnings
Key words |
Use |
All |
To suppress all warnings |
Boxing |
To suppress warnings relative to boxing/unboxing operations |
Cast |
To suppress warnings relative to cast operations |
Dep-ann |
To suppress warnings relative to deprecated annotation |
Deprecation |
To suppress warnings relative to deprecation |
Fallthrough |
To suppress warnings relative to missing breaks in switch statements |
Finally |
To suppress warnings relative-finally block that don ' t return |
hiding |
To suppress warnings relative to locals that hide variable |
Incomplete-switch |
To suppress warnings relative to missing entries in a switch statement (enum case) |
Nls |
To suppress warnings relative to non-nls string literals |
Null |
To suppress warnings relative to null analysis |
Rawtypes |
To suppress warnings relative to un-specific types if using generics on class params |
Restriction |
To suppress warnings relative to usage of discouraged or forbidden references |
Serial |
To suppress warnings relative to missing serialversionuid field for a serializable class |
Static-access |
o Suppress warnings relative to incorrect static access |
Synthetic-access |
To suppress warnings relative to unoptimized access from inner classes |
Unchecked |
To suppress warnings relative to unchecked operations |
Unqualified-field-access |
To suppress warnings relative to field access unqualified |
Unused |
To suppress warnings relative to unused code |
V. Java LINT Options
1. Meaning of Lint
Used to perform additional checks in more detail during the process of compiling the program.
2. Standard and non-standard options for Javac
standard option: refers to the options that are supported in the current and future versions, such as -CP and- D.
Non-standard options: refers to options that are supported by the current version, but are not necessarily supported in the future. View the non-standard options supported by the current version through Javac-x.
3. View the warning message
By default, execution Javac only displays the main message of the warning, but also prevents the compilation process. To see the details of the warning, you need to execute javac-xlint:keyword to compile the source code.
Vi. Summary
Now no longer afraid don't know set breakpoints No!
Java @SuppressWarnings Annotations