Defective Android arithmetic

Java files:

Package com.example.dell_pc.homework;

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.Random;

public class Mainactivity extends Appcompatactivity {
private int A;
private int B;
private int C;
private int D;
private int sy;
Private TextView TV;
Private Button btn_1;
Private Button btn_2;

@Override
protected void OnCreate (Bundle savedinstancestate) {
Super.oncreate (savedinstancestate);
Setcontentview (R.layout.activity_main);
Get Textview,button Object
TV = (TextView) Super.findviewbyid (R.ID.TEXTVIEW5);
btn_1 = (Button) Super.findviewbyid (r.id.btn_1);
Btn_2 = (Button) Super.findviewbyid (r.id.btn_2);
Random ();
View ();

Btn_2.setonclicklistener (New Button.onclicklistener () {
@Override

Algorithm
public void OnClick (View v) {

Switch (SY) {
Case 1:
Tv.settext (A + "+" + B + "-" + C + "*" +d+ "=?");
Break
Case 2:
Tv.settext (A + "-" + B + "*" + C + "/" + d+ "=?");
Break
Case 3:
Tv.settext (A + "*" + B + "+" + C + "-" + d+ "=?");
Break
Case 4:
Tv.settext (A + "/" + B + "-" + C + "+" + d+ "=?");
Break
Case 5:
Tv.settext (A + "+" + B + "/" + C + "+" + d+ "=?");
Break
Case 6:
Tv.settext (A + "+" + B + "/" + C + "+" + d+ "=?");
Break
Case 7:
Tv.settext (A + "-" + B + "/" + C + "*" + d+ "=?");
Break
}
}

});
Event Monitoring
Btn_1.setonclicklistener (New View.onclicklistener () {
public void OnClick (View v) {
Random ();
View ();
}
});
}

Generate a random number within 100
private void random () {
A = new Random (). Nextint (100);
b = new Random (). Nextint (100);
c = new Random (). Nextint (100);
sy = new Random (). Nextint (4);
}

private void View () {
Switch (SY) {
Case 1:
Tv.settext (A + "+" + B + "-" + C + "*" +d+ "=" + (a+b-c*d));
Break
Case 2:
Tv.settext (A + "-" + B + "*" + C + "/" + d+ "=" + (A-B*C/D));
Break
Case 3:
Tv.settext (A + "*" + B + "+" + C + "-" + d+ "=" + (a*b+c-d));
Break
Case 4:
Tv.settext (A + "/" + B + "-" + C + "+" + d+ "=" + (a/b-c+d));
Break
Case 5:
Tv.settext (A + "+" + B + "/" + C + "+" + d+ "=" + (a+b/c+d));
Break
Case 6:
Tv.settext (A + "+" + B + "/" + C + "+" + d+ "=" + (a+b/c+d));
Break
Case 7:
Tv.settext (A + "-" + B + "/" + C + "*" + d+ "=" + (a-b/c*d));
Break
}
}
}

Layout file:

<?xml version= "1.0" encoding= "Utf-8"?>
<relativelayout xmlns:android= "Http://schemas.android.com/apk/res/android"
Xmlns:tools= "Http://schemas.android.com/tools"
Android:id= "@+id/activity_main"
Android:layout_width= "Match_parent"
android:layout_height= "Match_parent"
android:paddingbottom= "@dimen/activity_vertical_margin"
android:paddingleft= "@dimen/activity_horizontal_margin"
android:paddingright= "@dimen/activity_horizontal_margin"
android:paddingtop= "@dimen/activity_vertical_margin"
tools:context= "Com.example.dell_pc.homework.MainActivity" >


<linearlayout
android:orientation= "Horizontal"
Android:layout_width= "Match_parent"
android:layout_height= "Match_parent"
android:layout_below= "@+id/textview5"
Android:layout_alignparentleft= "true"
Android:layout_alignparentstart= "true"
android:layout_margintop= "108DP" >

<button
android:text= "Next Question"
Android:layout_width= "Wrap_content"
android:layout_height= "Wrap_content"
Android:id= "@+id/btn_1"
android:layout_weight= "1"/>

<button
android:text= "Answer"
Android:layout_width= "Wrap_content"
android:layout_height= "Wrap_content"
Android:id= "@+id/btn_2"
android:layout_weight= "1"/>
</LinearLayout>

<textview
android:text= "TextView"
Android:layout_width= "Wrap_content"
android:layout_height= "Wrap_content"
Android:id= "@+id/textview5"
Android:layout_alignparenttop= "true"
Android:layout_centerhorizontal= "true"
android:layout_margintop= "38DP"/>
</RelativeLayout>

Defective Android arithmetic