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JDK5笔记

Posted on 2011-10-07 15:05 leekiang 阅读(404) 评论(0)  编辑  收藏 所属分类: java
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

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