Basic knowledge that Java beginners need to Master

Suddenly think of their own more than six months ago in a Web site to do some of the Java basic questions, was holding a full of confidence to go, the results found that a lot of basic knowledge is not understood or not fully understood. Some people learn programming from the application development began, which is very good, but there are always some small knowledge, we have not noticed, does not accumulate bujikuibu not even thousands of miles, I have encountered some of the listed out, I hope for some beginners some help:

1.0x indicates the number of 16 in the beginning, 0 indicates the number of 8

2. The decimal point of the floating-point type needs to be plus F, for example 0.2f

3.tracert Tracking routing commands, Tracert taobao.com can know the information during the search through the

which router hosts

4.JDK installation directory with two JRE files ((1) JRE folder under JDK directory

(2) The Java directory of the JRE folder is mainly used to do the development process of compiling

J.class file

5. After the container is reset, the components in the container of the FlowLayout layout manager

Size does not change as container size changes

6.public StringBuffer Test () {

StringBuffer buf=new StringBuffer ("");

try{

return Buf.append ("try");

}finally{

Buf.append ("finally");

}

}

return result is tryfinally

7. The statement that creates the criteria object is

Criteria C=session.createcriteria (User.class);

Spring AOP: Tight integration with Dependency injection

Implemented by means of proxy

Support for forward notification, surround notification,

Configured in <sop.config><aop:opintcut><aop:advisor> in previous versions of Spring2.0

(A little mistake)

8. The legitimate format of the user setting environment variable is: set Classpath=c:\jdk1.2\bin

The 9.URL class is included in the URI class

10.java source file compilation generated files called bytecode files

The result of 11.15.2%5 is 0.1999999999999993.

12. Garbage collection cannot be enforced

13.InputStreamReader belongs to character-oriented input stream

No Main method in 14.Applet program

The size of the array cannot be changed in 15.java

After 16.a=001001 executes a>>>3, a=1001010

17.thread object is not a direct-use hidden object contained in a JSP page

18. Each Unicode code occupies 16 bits

20.Float a=1.0 is the wrong method of assignment, and the correct one is float a=new float (1.0).

Or you can use float a=1.0f to create single-precision floating-point numbers.

21. In a system using hibernate, to delete a customer's data while deleting

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The user corresponds to all order data, and it is possible to configure the customer and Order Association Cascade property to all

The 22.java program generates byte code when compiled, which is a platform-independent binary code file

23.java Technology's Web server has Jboss,oc4j,websphere

The purpose of the 24.MVC design pattern is to better maintain the program

The character set used by the 25.java language is Unicode

26. The annotation statement that can support Javadoc is beginning with/** and ending with */

27. In object-oriented programming languages, a class is a separate program unit

28. When the thread calls the sleep () method, it cannot terminate the current thread's running

29. Call the Trim method to remove the space at the beginning and end of the string

30. In Java programming, Java directives are used to execute the. Class class file

31.constructor executes when an object is new

32. Unlike a while statement, the loop of a Do-while statement executes at least once

33. Class variable scope declares the variable's class