It's my first time using android studio and getting error? Don't know what seems to be wrong with it?

It's my First time using Android Studio. I'm creating an app that converts temperature, Area, and Length. I have four spinners as you can see, spinner one is for conversion type(temperature, Area, and Length) and spinner2, spinner3, and spinner4, has appropiate converter types for choosen converter category in spinner 1. I have a text field and a button called convert.

Now my app runs but after I selecting one of the conversion types it crashes and I get an error: "Unfortunately, UnitConverter has stopped"

I have included the LogCat error message.

Any help would be appreciated

Thank You

strings.xml for spinners:

<resources>
<string name="app_name">UnitConverter</string>
<string name="hello_world">Hello world!</string>
<string name="action_settings">Settings</string>

<string-array name="conversions">
    <item>Temperature</item>
    <item>Area</item>
    <item>Length</item>
</string-array>

<string-array name = "temperatureConverts">
    <item>From Celsius to Farenheit</item>
    <item>From Farenheit to Celsius</item>
</string-array>

<string-array name = "areaConverts">
    <item>From Square Feet to Square Meters</item>
    <item>From Square Meters to Square Feet</item>
</string-array>

<string-array name="LengthConverts">

    /*Feet to other converts*/
    <item>From Feet to Meters</item>
    <item>From Feet to Miles</item>
    <item>From Feet to Yards</item>

    /*Meters to other converts*/
    <item>From Meters to Feet</item>
    <item>From Meters to Miles</item>
    <item>From Meters to Yards</item>

    /*Miles to other converts*/
    <item>From Miles to Feet</item>
    <item>From Miles to Meters</item>
    <item>From Miles to Yards</item>

    /*Yards to other converts*/
    <item>From Yards to Feet</item>
    <item>From Yards to Meters</item>
    <item>From Yards to Mi</item>
</string-array>>

Design xml:

<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:tools="http://schemas.android.com/tools" android:layout_width="match_parent"
android:layout_height="match_parent" android:paddingLeft="@dimen/activity_horizontal_margin"
android:paddingRight="@dimen/activity_horizontal_margin"
android:paddingTop="@dimen/activity_vertical_margin"
android:paddingBottom="@dimen/activity_vertical_margin" tools:context=".ConverterActivity"
android:id="@+id/UnitConverter">

<EditText
    android:layout_width="match_parent"
    android:layout_height="wrap_content"
    android:inputType="numberDecimal"
    android:ems="10"
    android:id="@+id/numberEditText"
    android:layout_alignParentTop="true"
    android:layout_alignParentLeft="true"
    android:layout_alignParentStart="true"
    android:hint="Enter a Number" />

<TextView
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:textAppearance="?android:attr/textAppearanceMedium"
    android:id="@+id/editText"
    android:text="Select a Conversion Type"
    android:layout_below="@+id/numberEditText"
    android:layout_centerHorizontal="true" />

<Spinner
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:id="@+id/spinner1"
    android:entries ="@array/conversions"
    android:layout_below="@+id/editText"
    android:layout_alignParentLeft="true"
    android:layout_alignParentStart="true" />

<TextView
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:textAppearance="?android:attr/textAppearanceMedium"
    android:text=" "
    android:id="@+id/someText"
    android:layout_above="@+id/spinner2"
    android:layout_centerHorizontal="true"
    android:visibility="invisible"/>


<Spinner
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:id="@+id/spinner2"
    android:entries="@array/temperatureConverts"
    android:layout_alignBaseline="@+id/spinner3"
    android:layout_alignBottom="@+id/spinner3"
    android:layout_alignParentLeft="true"
    android:layout_alignParentStart="true"
    android:visibility="invisible"
/>

<Spinner
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:id="@+id/spinner3"
    android:entries="@array/areaConverts"
    android:visibility="invisible"
    android:layout_alignBaseline="@+id/spinner4"
    android:layout_alignBottom="@+id/spinner4"
    android:layout_alignParentLeft="true"
    android:layout_alignParentStart="true"
    />

<Spinner
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:id="@+id/spinner4"
    android:entries="@array/LengthConverts"
    android:visibility="invisible"
    android:layout_centerVertical="true"
    android:layout_alignParentLeft="true"
    android:layout_alignParentStart="true" />


<Button
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:text="NEXT"
    android:id="@+id/convertButton"
    android:onClick="convert"
    android:layout_below="@+id/spinner2"
    android:layout_centerHorizontal="true"
    android:layout_marginTop="41dp" />

</RelativeLayout>

activity class:

package uc.unitconverter;

import android.support.v7.app.AppCompatActivity; 
import android.os.Bundle;
import android.view.Menu;
import android.view.MenuItem;
import android.view.View;
import android.widget.ArrayAdapter;
import android.widget.Button;
import android.widget.EditText;
import android.widget.RadioButton;
import android.widget.Spinner;
import android.widget.TextView;

public class ConverterActivity extends AppCompatActivity {

Spinner spinner1;
Spinner spinner2;
Spinner spinner3;
Spinner spinner4;
EditText temp;
TextView someText;
Button convertButton;

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

    spinner1 = (Spinner)findViewById(R.id.spinner1);
    spinner2 = (Spinner)findViewById(R.id.spinner2);
    spinner3 = (Spinner)findViewById(R.id.spinner3);
    spinner4 = (Spinner)findViewById(R.id.spinner4);

    temp = (EditText)findViewById(R.id.numberEditText);
    someText = (TextView)findViewById(R.id.someText);


}

@Override
public boolean onCreateOptionsMenu(Menu menu) {
    // Inflate the menu; this adds items to the action bar if it is present.
    getMenuInflater().inflate(R.menu.menu_converter, menu);
    return true;
}

@Override
public boolean onOptionsItemSelected(MenuItem item) {
    // Handle action bar item clicks here. The action bar will
    // automatically handle clicks on the Home/Up button, so long
    // as you specify a parent activity in AndroidManifest.xml.
    int id = item.getItemId();

    //noinspection SimplifiableIfStatement
    if (id == R.id.action_settings) {
        return true;
    }

    return super.onOptionsItemSelected(item);
}


public void convert(View v) {

    double value = Double.valueOf(temp.getText().toString());

    String whichConversion = spinner1.getSelectedItem().toString();
    String whichTemperatureConversion = spinner2.getSelectedItem().toString();
    String whichAreaConversion = spinner3.getSelectedItem().toString();
    String whichLengthConversion = spinner4.getSelectedItem().toString();

    if(whichConversion.equals("Temperature"))
    {
        someText.setText(("Select Temperature Converters and Press Next"));
        someText.setVisibility(View.VISIBLE);
        spinner2.setVisibility(View.VISIBLE);

        convertButton.setText("Convert");

        if(whichTemperatureConversion.equals("From Celsius to Farenheit")) {
            value=UnitConverter.celsiusToFahrenheit(value);
        }
        else {
            value=UnitConverter.fahrenheitToCelsius(value);
        }

    }
    else if(whichConversion.equals("Area"))
    {

        someText.setText("Select Area Converters and Press Next");
                someText.setVisibility(View.VISIBLE);
        spinner3.setVisibility(View.VISIBLE);
        convertButton.setText("Convert");

        if(whichAreaConversion.equals("From Square Feet to Square Meters")) {
            value =UnitConverter.squareFeetToSquareMeters(value);
        }
        else {
            value =UnitConverter.squareMetersToSquareFeet(value);
        }
    }
    else
    {
        someText.setText("Select Length Converters and Press Next");
        someText.setVisibility(View.VISIBLE);
        spinner4.setVisibility(View.VISIBLE);
        convertButton.setText("Convert");

        if(whichLengthConversion.equals("From Feet to Meters")) {
            value=UnitConverter.feetToMeters(value);
        }
        else if(whichLengthConversion.equals("From Feet to Miles")){
            value=UnitConverter.feetToMiles(value);
        }
        else if(whichLengthConversion.equals("From Feet to Yards")) {
            value=UnitConverter.feetToYards(value);
        }
        else if(whichLengthConversion.equals("From Meters to Feet")) {
            value=UnitConverter.metersToFeet(value);
        }
        else if(whichLengthConversion.equals("From Meters to Miles")) {
            value=UnitConverter.metersToMiles(value);
        }
        else if(whichLengthConversion.equals("From Meters to Yards")) {
            value=UnitConverter.metersToYards(value);
        }
        else if(whichLengthConversion.equals("From Miles to Feet")){
            value=UnitConverter.milesToFeet(value);
        }
        else if(whichLengthConversion.equals("From Miles to Meters")) {
            value=UnitConverter.milesToMeters(value);
        }
        else if(whichLengthConversion.equals("From Miles to Yards")) {
            value=UnitConverter.milesToYards(value);
        }
        else if(whichLengthConversion.equals("From Yards to Feet")) {
            value=UnitConverter.yardsToFeet(value);
        }
        else if(whichLengthConversion.equals("From Yards to Meters")) {
            value=UnitConverter.yardsToMeters(value);
        }
        else{
            value=UnitConverter.yardsToMiles(value);
        }
    }

    temp.setText(Double.toString(value));

}


}

Class UnitConverters:

package uc.unitconverter;


public class UnitConverter {

/*********************** Length *****************************/
public static double celsiusToFahrenheit(double c){
    return 32+c*9/5;
}
public static double fahrenheitToCelsius(double f){
    return (f-32)*5/9;
}

/*********************** Length *****************************/
public static double squareMetersToSquareFeet(double sm){
    return ((sm * sm) * 10.76);
}
public static double squareFeetToSquareMeters(double sf) {
    return ((sf * sf) * 10.76);
}

/*********************** Length *****************************/
public static double feetToMeters(double feet) { return (feet * 0.3048); }
public static double feetToMiles(double feet) { return (feet * 0.00189394); }
public static double feetToYards(double feet) { return (feet * 0.3333); }
public static double metersToFeet(double meters) { return (meters * 3.28084); }
public static double metersToMiles(double meters) { return (meters * 0.000621371); }
public static double metersToYards(double meters) {return (meters * 1.09361);   }
public static double milesToFeet(double miles){return (miles * 5280);}
public static double milesToMeters(double miles) { return (miles * 1609.34); }
public static double milesToYards(double miles) { return (miles * 1760); }
public static double yardsToFeet(double yards) { return (yards * 3); }
public static double yardsToMeters(double yards) { return (yards * 0.9144); }
public static double yardsToMiles(double yards) { return (yards * 0.000568182); }
}

LogCat:

   '--------- beginning of crash
   09-19 11:40:43.033  21507-21507/? E/AndroidRuntime﹕ FATAL EXCEPTION: main
Process: uc.unitconverter, PID: 21507
java.lang.IllegalStateException: Could not execute method of the activity
        at android.view.View$1.onClick(View.java:4020)
        at android.view.View.performClick(View.java:4780)
        at android.view.View$PerformClick.run(View.java:19866)
        at android.os.Handler.handleCallback(Handler.java:739)
        at android.os.Handler.dispatchMessage(Handler.java:95)
        at android.os.Looper.loop(Looper.java:135)
        at android.app.ActivityThread.main(ActivityThread.java:5254)
        at java.lang.reflect.Method.invoke(Native Method)
        at java.lang.reflect.Method.invoke(Method.java:372)
        at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:903)
        at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:698)
 Caused by: java.lang.reflect.InvocationTargetException
        at java.lang.reflect.Method.invoke(Native Method)
        at java.lang.reflect.Method.invoke(Method.java:372)
        at android.view.View$1.onClick(View.java:4015)