Question

In: Computer Science

I need the JAVA code for a 4 function calculator app on andriod studio - The...

I need the JAVA code for a 4 function calculator app on andriod studio -

The requirements are the following :

- The only buttons needed are 0-9, *, /, +, -, a clear, and enter button

- Implement the onclicklistener on the main activity

- The calcuator should use order of operations (PEMDAS)

- It should be able to continue from a previous answer (Ex: If you type 2+6 the calculator will display 8. If you then multiple by 2 the current result will simply be multiplied by 2)

- It should read the entire sequence of numbers and operators and save them into a String. The information can be read out of the String using a StringTokenizer. The delimiters will be the operators on the calculator.

- The entire mathematical expression will be displayed on the screen before the equal button is clicked.

- The equation will simply be evaluated in the order that the user types in the numbers rather than the precedence

- If the user enters an equation with invalid syntax, the output should display “error”. The calculator should also display “error” for any mathematical calculations that are impossible.

Solutions

Expert Solution

import java.util.Scanner;

public class Calculator {

    public static void main(String[] args) {

        Scanner reader = new Scanner(System.in);
        System.out.print("Enter two numbers: ");

        // nextDouble() reads the next double from the keyboard
        double first = reader.nextDouble();
        double second = reader.nextDouble();

        System.out.print("Enter an operator (+, -, *, /): ");
        char operator = reader.next().charAt(0);

        double result;

        switch(operator)
        {
            case '+':
                result = first + second;
                break;

            case '-':
                result = first - second;
                break;

            case '*':
                result = first * second;
                break;

            case '/':
                result = first / second;
                break;

            // operator doesn't match any case constant (+, -, *, /)
            default:
                System.out.printf("Error! operator is not correct");
                return;
        }

        System.out.printf("%.1f %c %.1f = %.1f", first, operator, second, result);
    }
}
<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    tools:context=".MainActivity"
    android:orientation="vertical"
    android:weightSum="100">

    <TextView
        android:id="@+id/display"
        android:layout_width="match_parent"
        android:layout_height="0px"
        android:layout_weight="15"
        android:text=""
        app:layout_constraintBottom_toBottomOf="parent"
        app:layout_constraintLeft_toLeftOf="parent"
        app:layout_constraintRight_toRightOf="parent"
        app:layout_constraintTop_toTopOf="parent" />

    <LinearLayout
        android:layout_width="match_parent"
        android:layout_height="0px"
        android:layout_weight="20"
        android:orientation="horizontal"
        android:weightSum="100">

        <Button
            android:id="@+id/buttonadd"
            android:layout_width="0px"
            android:layout_height="match_parent"
            android:layout_weight="25"
            android:text="+"/>

        <Button
            android:id="@+id/button7"
            android:layout_width="0px"
            android:layout_height="match_parent"
            android:layout_weight="25"
            android:text="7"/>
        <Button
            android:id="@+id/button8"
            android:layout_width="0px"
            android:layout_height="match_parent"
            android:layout_weight="25"
            android:text="8"/>
        <Button
            android:id="@+id/button9"
            android:layout_width="0px"
            android:layout_height="match_parent"
            android:layout_weight="25"
            android:text="9"/>
    </LinearLayout>

    <LinearLayout
        android:layout_width="match_parent"
        android:layout_height="0px"
        android:layout_weight="20"
        android:orientation="horizontal"
        android:weightSum="100">

        <Button
            android:id="@+id/buttonsubtract"
            android:layout_width="0px"
            android:layout_height="match_parent"
            android:layout_weight="25"
            android:text="-"/>

        <Button
            android:id="@+id/button4"
            android:layout_width="0px"
            android:layout_height="match_parent"
            android:layout_weight="25"
            android:text="4"/>
        <Button
            android:id="@+id/button5"
            android:layout_width="0px"
            android:layout_height="match_parent"
            android:layout_weight="25"
            android:text="5"/>
        <Button
            android:id="@+id/button6"
            android:layout_width="0px"
            android:layout_height="match_parent"
            android:layout_weight="25"
            android:text="6"/>
    </LinearLayout>

    <LinearLayout
        android:layout_width="match_parent"
        android:layout_height="0px"
        android:layout_weight="20"
        android:orientation="horizontal"
        android:weightSum="100">

        <Button
            android:id="@+id/buttonmultiply"
            android:layout_width="0px"
            android:layout_height="match_parent"
            android:layout_weight="25"
            android:text="*"/>

        <Button
            android:id="@+id/button1"
            android:layout_width="0px"
            android:layout_height="match_parent"
            android:layout_weight="25"
            android:text="1"/>
        <Button
            android:id="@+id/button2"
            android:layout_width="0px"
            android:layout_height="match_parent"
            android:layout_weight="25"
            android:text="2"/>
        <Button
            android:id="@+id/button3"
            android:layout_width="0px"
            android:layout_height="match_parent"
            android:layout_weight="25"
            android:text="3"/>
    </LinearLayout>


    <LinearLayout
        android:layout_width="match_parent"
        android:layout_height="0px"
        android:layout_weight="20"
        android:orientation="horizontal"
        android:weightSum="100">

        <Button
            android:id="@+id/buttondivide"
            android:layout_width="0px"
            android:layout_height="match_parent"
            android:layout_weight="25"
            android:text="/"/>

        <Button
            android:id="@+id/buttonclear"
            android:layout_width="0px"
            android:layout_height="match_parent"
            android:layout_weight="25"
            android:text="Clear"/>
        <Button
            android:id="@+id/button0"
            android:layout_width="0px"
            android:layout_height="match_parent"
            android:layout_weight="25"
            android:text="0"/>
        <Button
            android:id="@+id/buttonequals"
            android:layout_width="0px"
            android:layout_height="match_parent"
            android:layout_weight="25"
            android:text="="/>
    </LinearLayout>
</LinearLayout>

for java

package com.example.10012698.calculatorproject;

import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.view.View;
import android.widget.Button;
import android.widget.TextView;

import java.util.ArrayList;
import java.util.StringTokenizer;
public class MainActivity extends AppCompatActivity implements View.OnClickListener {

Button button0, button1, button2, button3, button4, button5, button6,
button7, button8, button9, buttonadd, buttonsubtract, buttonmultiply,
buttondivide, buttonequals, buttonclear;
TextView display;
String displaytext="";
double result;
double x, y;
ArrayList<String> list;


@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);

button0 = (Button) findViewById(R.id.button0);
button1 = (Button) findViewById(R.id.button1);
button2 = (Button) findViewById(R.id.button2);
button3 = (Button) findViewById(R.id.button3);
button4 = (Button) findViewById(R.id.button4);
button5 = (Button) findViewById(R.id.button5);
button6 = (Button) findViewById(R.id.button6);
button7 = (Button) findViewById(R.id.button7);
button8 = (Button) findViewById(R.id.button8);
button9 = (Button) findViewById(R.id.button9);
buttonadd = (Button) findViewById(R.id.buttonadd);
buttonsubtract = (Button) findViewById(R.id.buttonsubtract);
buttonmultiply = (Button) findViewById(R.id.buttonmultiply);
buttondivide = (Button) findViewById(R.id.buttondivide);
buttonclear = (Button) findViewById(R.id.buttonclear);
buttonequals = (Button) findViewById(R.id.buttonequals);
display = (TextView) findViewById(R.id.display);
display.setOnClickListener(this);
list = new ArrayList<>();
}

public void onClick(View view)
{
if(!(view.equals(buttonclear)&&!(view.equals(buttonequals))))
{
display.setText(display.getText()+""+((Button)view).getText());

if(displaytext.equals("0"))
{
display.setText(" ");
}

if(view.equals(buttonclear))
{
display.setText(" ");
}

if(view.equals(buttonequals))
{
displaytext= displaytext.substring(0,displaytext.length()-1);
StringTokenizer operators= new StringTokenizer(displaytext, "+-*/",true);

while(operators.hasMoreTokens())
{
list.add(operators.nextToken());
}

for(int j=0; j<list.size()-1; j++)
{
if (list.get(j).equals("*") || list.get(j).equals("/"))
{
x = Double.parseDouble(list.get(j - 1));
y = Double.parseDouble(list.get(j + 1));

if (list.get(j).equals("*"))
{
result+=(x*y);
}

if (list.get(j).equals("/"))
{
result+=(x/y);
}
}
}
for(int k=0;k<list.size()-1;k++)
{
if (list.get(k).equals("+") || list.get(k).equals("-"))
{
x = Double.parseDouble(list.get(k - 1));
y = Double.parseDouble(list.get(k + 1));

if (list.get(k).equals("+"))
{
result+=(x+y);
}

if (list.get(k).equals("-"))
{
result+=(x-y);
}
}
}
}
display.setText(""+result);


}
}

this is the program for java code for calculator


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