# Java Compiler Errors/Warnings Preferences

Indicate your preferences for the Errors/Warnings settings on the Java > Compiler > Errors/Warnings preference page.

### Code style

Option | Description | Default
--- | --- | ---
Non-static access to a static member | When enabled, the compiler will issue an error or a warning whenever a static field or method is accessed with an expression receiver. A reference to a static member should be qualified with a type name. | Warning
Indirect access to a static member | When enabled, the compiler will issue an error or a warning whenever a static field or method is indirectly accessed. A static field of an interface should be qualified with the declaring type name. | Ignore
Unqualified access to instance field | When enabled, the compiler will issue an error or a warning whenever it encounters a field access which is not qualified (e.g. misses a 'this'). | Ignore
Undocumented empty block | When enabled, the compiler will issue an error or a warning whenever it encounters an empty block statement with no explaining comment. | Ignore
Access to a non-accessible member of an enclosing type | When enabled, the compiler will issue an error or a warning whenever it emulates access to a non-accessible member of an enclosing type. Such accesses can have performance implications. | Ignore
Method with a constructor name | Naming a method with a constructor name is generally considered poor style programming. When this option is enabled, the compiler will signal such scenario either as an error or a warning. | Warning
Parameter assignment | Assigning a value to a parameter is generally considered poor style programming. When this option is enabled, the compiler will signal such scenario either as an error or a warning. | Ignore
Non-externalized strings | When enabled, the compiler will issue an error or a warning for non externalized String literal (i.e. non tagged with //$NON-NLS-<n>$) or for non externalized String tags which do not belong to a String. | Ignore

### Potential programming problems

Serializable class without serialVersionUID | When enabled, the compiler will issue an error or a warning whenever a type implementing 'java.io.Serializable' does not contain a serialVersionUID field. | Warning
Assignment has no effect (e.g. 'x = x') | When enabled, the compiler will issue an error or a warning whenever an assignment has no effect (e.g. 'x = x'). | Warning
Possible accidental boolean assignment (e.g. 'if (a = b)') | When enabled, the compiler will issue an error or a warning whenever it encounters a possible accidental boolean assignment (e.g. 'if (a = b)'). | Ignore
'finally' does not complete normally | When enabled, the compiler will issue an error or a warning whenever a 'finally' statement does not complete normally (e.g. contains a return statement). | Warning
Empty statement | When enabled, the compiler will issue an error or a warning whenever it encounters an empty statement (e.g. a superfluous semicolon). | Ignore
Using a char array in string concatenation | When enabled, the compiler will issue an error or a warning whenever a char[] expression is used in String concatenations, `"hello" + new char[]{'w','o','r','l','d'}` | Warning
Hidden catch blocks | Locally to a try statement, some catch blocks may hide others , e.g. `try { throw new java.io.CharConversionException();` `} catch (java.io.CharConversionException e) {` `} catch (java.io.IOException e) {}.` When enabled, the compiler will issue an error or a warning for hidden catch blocks corresponding to checked exceptions. | Warning
Inexact type match for vararg arguments | When enabled, the compiler will issue an error or a warning whenever it encounters an inexact type match for vararg arguments. | Warning
Boxing and unboxing conversions | When enabled, the compiler will issue an error or a warning whenever it encounters a boxing or unboxing conversion. Autoboxing may affects performance negatively. | Ignore
Enum type constant not covered on 'switch' | When enabled, the compiler will issue an error or a warning whenever it encounters a switch statement which does not contain case statements for every enum constant of the referenced enum. | Ignore
'switch' case fall-through | When enabled, the compiler will issue an error or a warning whenever it encounters a switch case without a 'break' statement. Empty switch cases are allowed. | Ignore
Null pointer access | When enabled, the compiler will issue an error or a warning when it encounters that a local variable which is certainly null is dereferenced. Note that the analysis can not find all null pointer accesses, see Potential null pointer access. | Warning
Potential null pointer access | When enabled, the compiler will issue an error or a warning when it encounters that a local variable which may be null is dereferenced. Note that the analysis is fairly conservative, it only considers cases where there is something suspicious. | Ignore

### Name shadowing and conflicts

Field declaration hides another field or variable | When enabled, the compiler will issue an error or a warning if a field declaration hides another inherited field. | Ignore
Local variable declaration hides another field or variable | When enabled, the compiler will issue an error or a warning if a local variable declaration hides another field or variable. | Ignore
Include constructor or setter method parameters | When enabled, the compiler additionally will issue an error or a warning if a constructor or setter method parameter hides another field or variable. | Off
Type parameter hides another type | When enabled, the compiler will issue an error or a warning if i.e. a type parameter of an inner class hides an outer type. | Warning
Method does not override package visible method | A package default method is not visible in a different package, and thus cannot be overridden. When this option is enabled, the compiler will signal such scenario either as an error or a warning. | Warning
Interface method conflicts with protected 'Object' method | When enabled, the compiler will issue an error or a warning whenever an interface defines a method incompatible with a non-inherited Object method. Until this conflict is resolved, such an interface cannot be implemented, e.g. `interface I {` `int clone();` `}` | Warning

### Deprecated and restricted API

Deprecated API | When enabled, the compiler will signal use of deprecated API either as an error or a warning. | Warning
Signal use of deprecated API inside deprecated code | When enabled, the compiler will signal use of deprecated API inside deprecated code. The severity of the problem is controlled with option "Deprecated API". | Off
Signal overriding or implementing deprecated method | When enabled, the compiler will signal overriding or implementing a deprecated method The severity of the problem is controlled with option "Deprecated API". | Off
Forbidden reference (access rules) | When enabled, the compiler will signal a forbidden reference specified in the access rules. | Error
Discouraged reference (access rules) | When enabled, the compiler will signal a discouraged reference specified in the access rules. | Warning

### Unnecessary code

Local variable is never read | When enabled, the compiler will issue an error or a warning whenever a local variable is declared but never used within its scope. | Warning
Parameter is never read | When enabled, the compiler will issue an error or a warning whenever a parameter is declared but never used within its scope. | Ignore
Ignore in overriding and implementing methods | When enabled, the compiler will not issue an error or a warning whenever a parameter is declared but never used within its scope in a method that overrides or implements another method. | On
Ignore parameters documented with '@param' tag | When enabled, the compiler will not issue an error or a warning whenever an unread parameter is documented with an '@param' tag. | On
Unused import | When enabled, the compiler will issue an error or a warning for unused import reference. | Warning
Unused local or private members | When enabled, the compiler will issue an error or a warning whenever a local or private member is declared but never used within the same unit. | Warning
Redundant null check | When enabled, the compiler will issue an error or a warning whenever a local variable which can not be null is tested for null. | Ignore
Unnecessary 'else' statement | When enabled, the compiler will issue an error or a warning whenever it encounters an unnecessary else statement (e.g. if (condition) return; else doSomething();). | Ignore
Unnecessary cast or 'instanceof' operation | When enabled, the compiler will issue an error or a warning whenever it encounters an unnecessary cast or 'instanceof' operation (e.g. if (object instanceof Object) return;). | Ignore
Unnecessary declaration of thrown exception | When enabled, the compiler will issue an error or a warning whenever it encounters an unnecessary declaration of a thrown exception. | Ignore
Ignore in overriding and implementing methods | When enabled, the compiler will not issue an error or a warning whenever it encounters an unnecessary declaration of a thrown exception in a method that overrides or implements another method. | On
Ignore exceptions documented with '@throws' or '@exception' tags | When enabled, the compiler will not issue an error or a warning whenever an an unnecessary declaration of a thrown exception is documented with an '@throws' or '@exception' tag. | On
Ignore 'Exception' and 'Throwable' | When enabled, the compiler will not issue an error or a warning whenever it encounters an unnecessary declaration of 'Exception' and 'Throwable' exception | On
Unused 'break' or 'continue' label | When enabled, the compiler will issue an error or a warning whenever it encounters an unused 'break' or 'continue' label. | Warning
Redundant super interface | When enabled, the compiler will issue an error or a warning whenever it encounters a type which explicitly implements an interface that is already implemented by any of its supertypes. | Ignore

### Generic types

Unchecked generic type operation | When enabled, the compiler will issue an error or a warning whenever it encounters an unchecked generic type operation. | Warning
Usage of a raw type | When enabled, the compiler will issue an error or a warning whenever it encounters a usage of a raw type (i.e. List instead of List<String>). | Warning
Generic type parameter declared with a final type bound | When enabled, the compiler will issue an error or a warning whenever it encounters a type bound involving a final type. | Warning

### Annotations

Missing '@Override' annotation | When enabled, the compiler will issue an error or a warning whenever it encounters a method overriding another implemented method, and the '@Override' annotation is missing. | Ignore
Missing '@Deprecated' annotation | When enabled, the compiler will issue an error or a warning whenever it encounters a deprecated type without additional '@Deprecated' annotation. | Ignore
Annotation is used as super interface | When enabled, the compiler will issue an error or a warning whenever it encounters a type implementing an annotation. Although possible, this is considered bad practice. | Warning
Unhandled token in '@SuppressWarnings' | When enabled, the compiler will issue an error or a warning whenever it encounters an unhandled token in a '@SuppressWarnings' annotation. | Warning
Unused '@SuppressWarnings' token | When enabled, the compiler will issue an error or a warning whenever it encounters an unused token in a '@SuppressWarnings' annotation. | Warning
Enable '@SuppressWarnings' annotations | When enabled, the compiler will process '@SuppressWarnings' annotations. | On

When Treat errors like fatal compile errors is enabled, all generated errors, fatal or configurable, lead to non-executable code. If disabled, then your code can be executed as long as it has no fatal error (i.e. syntax error).

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