??????????????JDK??????????http://www.oracle.com/technetwork/java/javase/downloads/index.html
??????????JDK
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????1.???????????????????????á?????????????????

????2.???????????????????????“?????????”???????“??????”?????????“JAVA_HOME”????“?????”?????????JDK????·??????JDK????·?????????????·?????C:Program FilesJavajdk1.7.0_21?????????????????????

????3.??“??????”????????в?PATH????????????????????????? PATH????????и??????????“??”???????“?????”?????????λ???? ??“%JAVA_HOME%in;%JAVA_HOME%jrein;”?????????“%JAVA_HOME%in;”?????????????;????????????????????????