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Expression4J

Sample > Simple expression

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Simple expression
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Create an expression

An expression is constitued by :

function name (like f or foo or function)
parameters (like x or y or foo)
equal sign (=)
the body of the expression (like 2+3*x or 3.5e-2+4)

Expression does not support space. If spaces are present in the expression, the parsin will generate an error.

My first expression with expression4j

The next example create a simple expression with no parameter


 2: try { 
 3: Expression expression = ExpressionFactory.createExpression("f()=2.4e-2");
 4: System.out.println("Expression name: " + expression.getName());
 5: System.out.println("Value of expression:" + expression.evaluate(null)
.getRealValue())
 6: }
 7: catch (Exception e) {
 8: System.out.println("Error: " + e);
 9: }

Line 3 define the expression "f". This expression has no parameter and is equal to the constant 2.4e-2.
Line 4 display the name of the expression after the parsing. This line must display the result:

Expression name: f

Line 5 evaluate the expression and display the résult. The result must be:

Value of expression:0.024