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 Multiplication Design a recursive function that accepts two arguments into the parameters x and y. The function should return the value of x times y. Remember, multiplication can be performed as repeated addition as follows: 7×4=4+4+4+4+4+4+4(To keep the function simple, assume that x and y will always hold positive nonzero integers.)

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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Recursive Multiplication Design a recursive function that accepts two arguments into the parameters x and y. The function should return the value of x times y. Remember, multiplication can be performed as repeated addition as follows: 7×4=4+4+4+4+4+4+4(To keep the function simple, assume that x and y will always hold positive nonzero integers.)

JAVA LANGUAGE CODE Postfix Calculator by CodeChum Admin One good implementation of computing infix expressions is to transform them to postfix and then evaluate via the postfix expression. Infix expressions is the common way of writing arithmetic expressions. The binary operator come between them as shown below: 2 * 5 + 9 - 10 / 20 In postfix expressions, the operands come first before the operator: 2 5 * 9 + 10 20 / - A stack can be used to evaluate postfix expressions. The operands are pushed onto the Stack and when an operator is found two operands are popped and the operation is performed and finally the result is pushed back onto the Stack. The final answer will be the lone element of the Stack. Input The first line contains a positive integer n representing the number of postfix expressions. What follows are n postfix expressions themselves. 5 10 20 + 30 15 2 * + 100 20 30 + / 90 20 10 + + 0 / 9 3 - 10 + 2 * Output A single line containing the result of…

Recursive functions are ones that repeat themselves repeatedly.