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:1, EL get JSP four scope to save data (Access JavaBean properties)2. EL Expression Support operation3, EL built-in 11 objects---web development common objects4, EL call Java methodEl is included in the specification, javaee1.3 and previous versions from the javaee1.4 version, which is not parsed by default on El* If you want to javaee1.3 and previous version resolution EL------Set page Property Iselignored
An expression contains a + 、—、 *,/, () operator, to evaluate the value of an expression. Here the use of stacks, respectively, to store the operands and operators, the general idea is to use the double stack to convert infix expression to the suffix expression to calculate.1
Introduction of El ExpressionEL Full name is the main function of expression Language.el:Get Data:El Expressions are primarily used to replace script expressions in JSP pages to retrieve Java objects from various types of Web domains and get data. (objects in a web domain, accessing JavaBean properties, accessing the list collection, accessing the map collection, accessing an array)perform the operation:• U
what to do and how to do it is separated, which means that the Java collection now knows how to iterate, and the collection elements can be processed in parallel at the API level. In the following example, I'll show you how to iterate through a list using lambda or not using a lambda expression. You can see that the list now has a ForEach () method that iterates over all the objects and applies your lambda
Java expression Calculation
Expression calculation refers(34+2)*4*2+7The value of the expression, because it involves parentheses and operator priority, if it is difficult to calculate directly, follow(34+2)*4*2+7The normal order isInfix expressionTo convert the expressionSu
What is two fork tree, no longer introduced here, you can own Baidu: two fork tree. Use Java to implement "Expression binary tree" here.
Definition of expression binary tree
The first step is to understand the expression of the binary tree is what dongdong? Give me a chestnut, ex
(ActionEvent e) { System.out.println ("Without lambda expression is boring"); } });/ /Java 8 Way:show.addActionListener ((e), { System.out.println ("Action!! Lambda Expressions Rocks ");});In Java 8, you can use a lambda expression to replace an ugly anonymous class.3. Iterating through the lis
expression contains a string, it is another case: because the plus sign (+) is placed between the string and the base type value, the plus sign is a string join operator instead of an addition operation. look at the following code:Output String Hello!a7System.out.println ("hello!" + ' a ' + 7);Output String 104hello!System.out.println (' a ' + 7 + "hello!");for the first
Description
Example
Results
= = or EQ
Equals
${5==5} or ${5eq5}
True
! = or NE
Not equal to
${5!=5} or ${5ne5}
False
Less than
${3
True
> or GT
Greater than
${3>5} or {3GT5}
False
Less than or equal
${3
True
>= or GE
Greater than or equal
5} or ${3ge5}
False
Ex
Chapter II: lambda expression
The biggest change in Java8 is the introduction of lambda expressions, a compact way of passing behavior, which is what's left of the book, so let's go into it.
Write the first lambda expression
Swing is a platform-independent GUI library in which there are many common habits, such as registering an event listener to know what the user clicked on, and this event listener ca
EL expression in JSP _ dynamic node Java school arrangement, jspel
The JSP page supports EL expressions. The full name of EL is Expression Language. The main functions of EL expressions are:
① Obtain data;
② Perform operations;
③ 11 hidden objects using EL expressions;
④ Call the Java method.
Of course, EL expressions
Variables${test}when the current polygon does not specify a value below which scope, it will be found by default in the following order, and if none are found, output an empty stringpagescope --requestscope--Sessionscope-ApplicationscopeAuto-type conversions can be performed on the obtained values in 4.ELIf you get the values in Test1 and test2 as String values, you can do the math directly: ${test1 + test2}5. Get Request ParametersGET request parameters can be obtained by form or hyperlinkGene
The middle order expression is very intuitive to us (this is what we usually touch), but the computer is cumbersome to handle (parentheses, precedence, and so on), there are no parentheses in the pre-order and post-sequence expressions, and only one-way scanning is required in the calculation, and operator precedence is not considered. such as 2*3/(2-1) +3* (4-1)A pre-order
If you've ever used Perl or any other built-in regular expression-supported language, you know how simple it is to handle text and matching patterns with regular expressions. If you are unfamiliar with the term, then "regular expression" (Regular Expression) is a string of characters that defines a pattern for searching for a matching string.
Many languages, inc
, and operators. The latter three have a special meaning when encountered during the processing of a pattern.
Meta characters are a special means to describe single characters in the input text. A common example for a meta character is the dot '. ', which, when used in a regular expression, matches any character.
Character sets are a convenient means to describe different characters that match a single character in the input. character sets are enc
The example of this article describes the Java implementation of arbitrary arithmetic expression evaluation algorithm. Share to everyone for your reference. The specific analysis is as follows:
This program is used to compute arbitrary arithmetic expressions. The result of 4 * (10 + 2) + 1 should be 49.Algorithm Description:
1. First define operator precedence.
Meaning of expression:
1. Character
x character X. For example a denotes character a
\ backslash character. Write as \\\\ in writing. (Note: Because Java in the first parsing, the \\\\ parsing into a regular expression \ \, in the second resolution, and then resolved to \, so usually not 1.1 of the escape characters enumerated, including 1.1 of \, and with the
Public classTest { Public Static voidMain (string[] args) {intt = 0; intp = 0; intQ = 0; intTail = 1; intHead = 2; /*** this (t = = tail) expression is judged by the time the first T or the previous value is not copied, the second T is the value after the assignment * so this is not imagined false, but it will appear true * Pay attention to the details.*/P= (T! = (t = tail))?T:head; SYSTEM.OUT.PRINTLN (P
As we all know, in Java, the expression in the switch statement must be an integer or operator type. strings are used for branching and can only be opportunistic.
The first key is to use the String hasCode to obtain the String hash code. The hash code algorithm is as follows:
S [0] * 31 ^ (n-1) + s [1] * 31 ^ (n-2) +... + s [n-1]
Therefore, the hash codes of
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