[Original]java Web Learning note 39:el (arithmetic operator, relational operator, logical operator, empty operator, conditional operator, bracket operator)

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Arithmetic operators, relational operators, logical operators, empty operators, conditional operators, parentheses operators

1. Arithmetic Operations (5)

　　

　　

2. Relational operators (6)

　　

Attention

When using the EL relational operator, it cannot be written as:

${param.password1} = = ${param.password2}

Or

${${param.password1} = = ${Param.password2}}

and should be written

${Param.password1 = = Param.password2}

3. Logic operations (3)

　　

　　

4. Other

4.1 Empty operator

The ①empty operator is used primarily to determine whether a value is null or empty. In addition to variables, the operator can also act on the collection, if the collection does not exist or if there are no elements in the collection, the result is true

${Empty Param.name}

{Empty} A

4.2 Bar Operators

${A? B:C} means that when a is true, B is executed and A is false, C is executed

4.3 Parenthesis operator

1) The parentheses operator is primarily used to change the execution priority

(from high to low, from left to right)

　　　　

　　　　

[Original]java in Web Learning note 39:el (arithmetic operator, relational operator, logical operator, empty operator, conditional operator, bracket operator)