title: Modulus operation for array index
body: <p>I got a tutorial about using a button for switching some images, and here is the code</p>
  
  <pre><code>public class MainActivity extends AppCompatActivity {
  private static ImageView andro;
  private static Button buttonswitch;
  
  int current_image_index = 0;
  int[] images = {R.mipmap.andro_img,R.mipmap.apple_image,R.mipmap.ic_launcher,R.mipmap.ic_launcher_round};
  @Override
  protected void onCreate(Bundle savedInstanceState) {
      super.onCreate(savedInstanceState);
      setContentView(R.layout.activity_main);
      buttonClick();
  }
  public void buttonClick() {
      andro = (ImageView) findViewById(R.id.imageView);
      buttonswitch = (Button) findViewById(R.id.button);
      buttonswitch.setOnClickListener(
              new View.OnClickListener() {
                  @Override
                  public void onClick(View view) {
                      current_image_index++;
                      current_image_index = current_image_index % images.length;
                      andro.setImageResource(images[current_image_index]);
                  }
              }
      );
  }
  }
  </code></pre>
  
  <p>I got really confused in this part :</p>
  
  <pre><code> @Override
              public void onClick(View view) {
                  current_image_index++;
                  current_image_index = current_image_index % images.length;
                  andro.setImageResource(images[current_image_index]);
  </code></pre>
  
  <p>What I understand is that once I click the button, then the int current_image_index will increase by 1. Then modulus current_image_index with the images.length which will have the remainder of current_image_index divide by the image.length. For example, for the first time I will have current_image_index = 0, then once clicked, it will be 1, then current_image_index % image.length = 0. Then andro.setImageResource(images[0]);</p>
  
  <p>this will repeated again and again since the current_image_index stays to be 0. Then how can the picture changes constantly once it is clicked since the current_image_index%image.length will always give a result of 0.</p>