JDK5笔记

1，SuppressWarnings的作用是抑制编译器产生警告信息。
@SuppressWarnings("unused")
@SuppressWarnings("unchecked")

eclipse支持的 SuppressWarning的值如下，其他开发工具略有差异。

• 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 to 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
• 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 to 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

2，注解
注解是加入到java源代码中的一些描述性的数据，本身不能执行。可利用反射(当RetentionPolicy= RUNTIME)或文本解析取得注解信息。
@Target,@Retention为元注解。
SuppressWarnings的源码如下：

@Target({TYPE, FIELD, METHOD, PARAMETER, CONSTRUCTOR, LOCAL_VARIABLE})
@Retention(RetentionPolicy.SOURCE)
public  @ interface  SuppressWarnings {
    String[] value();
}

package  java.lang.annotation;

public   enum  RetentionPolicy {
     /**
     * Annotations are to be discarded by the compiler.
      */
    SOURCE,

     /**
     * Annotations are to be recorded in the class file by the compiler
     * but need not be retained by the VM at run time.  This is the default
     * behavior.
      */
    CLASS,

     /**
     * Annotations are to be recorded in the class file by the compiler and
     * retained by the VM at run time, so they may be read reflectively.
     *
     *  @see  java.lang.reflect.AnnotatedElement
      */
    RUNTIME
}

package  java.lang.annotation;
public   enum  ElementType {
    TYPE,
    FIELD,
    METHOD,
    PARAMETER,
    CONSTRUCTOR,
    LOCAL_VARIABLE,
    ANNOTATION_TYPE,
    PACKAGE
}

3，泛型

     public   < T >  T testT(List < T >   list){
        T t  = (T) list;
         return  t;
    }

4，自动装箱 （AutoBoxing）

关于row type
http://stackoverflow.com/questions/2770321/what-is-a-raw-type-and-why-shouldnt-we-use-it/
http://www.blogjava.net/sevenguin/archive/2011/04/20/348628.html

转：J2SE5中的最新注释功能SuppressWarnings
http://wenku.baidu.com/view/9d20440f844769eae009edf2.html
实战篇：设计自己的Annotation
Supported Values for @SuppressWarnings