Prefix Calculator Program plan: Include necessary header files. Define the class “PreficCalc”. Declare the necessary variables. Define the method “start()”. Create labels and text fields to enter the prefix expression. Create a button “evaluate” to submit and calculate the resultant value. Define the class “CmdTextListener”. Define the method “handle()”. Declare the string variable to get a prefix expression. Declare the method “buildExpr()” to read and build a binary tree. Declare the method “eval()” to evaluate the tree expression. Display the result into the resultant text field. Define the method “eval()” to evaluate the expression. The “if” statement check, left and right child of tree is equal to null. True, return the integer value. Otherwise, Call the method “eval()” and assign the result into “leftOp”. Call the method “eval()” and assign the result into “rightOp”. The “if” statement check, tree value is equal to “*”. True, return the multiplied value. The “if” statement check, tree value is equal to “+”. True, return the added value. Return “0”. Define the method “isNumber()”. If the given expression is number then, return the number itself. Define the class “Node”. Declare the necessary variables. Define the parameterized constructor. Define the method “buildExpr()” to read and build a binary tree. Read the input from the user. The “if” statement check the expression is number. True, return the node itself. Otherwise, build a non-leaf tree. Call the method “Node()” and return a value. Define the “main()” method. Declare the method “launch()” to call the “start()” method eventually.

Question

Recursive PrintingDesign a recursive function that accepts an integer argument,n , and prints the numbers 1 up through n .

Answer 1

Question

Chapter 21, Problem 4PC

Program Plan Intro

Prefix Calculator

Program plan:

Include necessary header files.

Define the class “PreficCalc”.

Declare the necessary variables.

Define the method “start()”.

Create labels and text fields to enter the prefix expression.

Create a button “evaluate” to submit and calculate the resultant value.

Define the class “CmdTextListener”.

Define the method “handle()”.

Declare the string variable to get a prefix expression.

Declare the method “buildExpr()” to read and build a binary tree.

Declare the method “eval()” to evaluate the tree expression.

Display the result into the resultant text field.

Define the method “eval()” to evaluate the expression.

The “if” statement check, left and right child of tree is equal to null.

True, return the integer value.

Otherwise,

Call the method “eval()” and assign the result into “leftOp”.

Call the method “eval()” and assign the result into “rightOp”.

The “if” statement check, tree value is equal to “*”.

True, return the multiplied value.

The “if” statement check, tree value is equal to “+”.

True, return the added value.

Return “0”.

Define the method “isNumber()”.

If the given expression is number then, return the number itself.

Define the class “Node”.

Declare the necessary variables.

Define the parameterized constructor.

Define the method “buildExpr()” to read and build a binary tree.

Read the input from the user.

The “if” statement check the expression is number.

True, return the node itself.

Otherwise, build a non-leaf tree.

Call the method “Node()” and return a value.

Define the “main()” method.

Declare the method “launch()” to call the “start()” method eventually.

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