SupressWarnings

Definition

The @SuppressWarnings annotation is defined in the Java Language Specification section 9.6.1.5. This section states:

The annotation type SuppressWarnings supports programmer control over warnings otherwise issued by the Java compiler. It contains a single element that is an array of String. If a program declaration is annotated with the annotation @SuppressWarnings(value = {S₁, ... , S_k}), then a Java compiler must not report any warning identified by one of S₁, ... , S_k if that warning would have been generated as a result of the annotated declaration or any of its parts.

Unchecked warnings are identified by the string "unchecked".

The subsequent section on @Deprecation also mentions that these warnings can be suppressed with@SuppressWarnings("deprecation").

Valid Warning Types

The only two warning strings that are mentioned in the specification itself are "unchecked" and "deprecation". However, the Sun JDK uses a larger set of strings in the compiler. You can determine the current set by executing:

javac -X

which will show you (among other things) the valid settings for -Xlint.

For example, Sun JDK 1.5 shows:

• all - suppress all warnings from this code
• deprecation - suppress warnings from using deprecated code
• unchecked - suppress warnings from an unchecked call or an unchecked cast
• fallthrough - suppress warnings if a switch falls through without finding a valid case (and no default)
• path -
• serial - suppress warnings if a Serializable class does not define a serialVersionUID
• finally - suppress warnings from return within a finally (which will ignore return with the try)

And Sun JDK 1.6 adds:

• cast
• divzero - suppress warnings if integer divide by zero is detected
• empty
• overrides
• none

IDEs and static analysis tools typically support a large number of other possible values for @SuppressWarnings. These values correspond to specific static analysis checks performed by the IDE.

Eclipse

The Eclipse warning values for Eclipse 3.3 are documented in the JDT docs.

• all - suppress all warnings
• boxing - suppress warnings relative to boxing/unboxing operations
• cast - suppress warnings relative to cast operations
• dep-ann - suppress warnings relative to deprecated annotation
• deprecation - suppress warnings relative to deprecation
• fallthrough - suppress warnings relative to missing breaks in switch statements
• finally - suppress warnings relative to finally block that don't return
• hiding - suppress warnings relative to locals that hide variable
• incomplete-switch - suppress warnings relative to missing entries in a switch statement (enum case)
• nls - suppress warnings relative to non-nls string literals
• null - suppress warnings relative to null analysis
• restriction - suppress warnings relative to usage of discouraged or forbidden references
• serial - suppress warnings relative to missing serialVersionUID field for a serializable class
• static-access - suppress warnings relative to incorrect static access
• synthetic-access - suppress warnings relative to unoptimized access from inner classes
• unchecked - suppress warnings relative to unchecked operations
• unqualified-field-access - suppress warnings relative to field access unqualified
• unused - suppress warnings relative to unused code

IntelliJ

NetBeans

Examples

An example of specifying a single warning:

@SuppressWarnings("unchecked")

public void methodWithScaryWarnings() {

List rawList = new ArrayList();

List stringList = (List)rawList;

}

An example of using two warnings:

@SuppressWarnings({"unchecked","deprecation"})
public void methodWithScaryWarnings() {

callDeprecatedMethod();

}

http://knol.google.com/k/suppresswarnings-annotation-in-java