java - How to iterate through an ArrayList

MainActivity.java

 package com.cfsuman.me.javaexamples;  import android.graphics.Color; import android.graphics.drawable.ColorDrawable; import android.support.v7.app.AppCompatActivity; import android.os.Bundle; import android.view.Window; import android.widget.RelativeLayout; import android.widget.TextView;  import java.util.ArrayList; import java.util.List; import java.util.Iterator;   public class MainActivity extends AppCompatActivity {      @Override     protected void onCreate(Bundle savedInstanceState) {         requestWindowFeature(Window.FEATURE_ACTION_BAR);         super.onCreate(savedInstanceState);         setContentView(R.layout.activity_main);          // Set background color for action kafetaria         getSupportActionBar().setBackgroundDrawable(new ColorDrawable(Color.RED));          // Get widget reference from XML layout         RelativeLayout rl = (RelativeLayout) findViewById(R.id.rl);         TextView tv = (TextView) findViewById(R.id.tv);          // Empty the TextView         tv.setText("");          // Initialize a new ArrayList         List<String> colors = new ArrayList<>();         // Add some elements to ArrayList         colors.add("Red");         colors.add("Green");         colors.add("Blue");         colors.add("Yellow");         colors.add("Black");          // Iterate through colors ArrayList         tv.setText(tv.getText() + "Colors : ");         for(int i=0;i<colors.size();i++){             tv.setText(tv.getText() + colors.get(i) + ", ");         }          // Another way to Iterate through ArrayList         tv.setText(tv.getText() + "\nColors : ");         Iterator it = colors.iterator();         while(it.hasNext()){             tv.setText(tv.getText() + "" + it.next() + ", ");         }          // Another way to iterate through ArrayList         tv.setText(tv.getText() + "\nColors : ");         for(String s : colors){             tv.setText(tv.getText() + s + ", ");         }          // Another way to iterate through ArrayList         tv.setText(tv.getText() + "\nColors : ");         int index = 0;         while(colors.size()>index){             tv.setText(tv.getText() + "" + colors.get(index) + ", ");             index++;         }          // Iterate over an ArrayList and check a value         // But, this will throw error if ArrayList contains null value         for(String s : colors){             if(s.equals("Blue")){                 tv.setText(tv.getText() + "\n\nWOW! Blue found.");             }         }          // Adding an empty value to ArrayList         colors.add("");         // Adding a null value to ArrayList         colors.add(null);         // Adding an element to ArrayList         colors.add("White");          // Iterate over ArrayList and check a value         String valueToCheck = "Black";         for(String s : colors){             // Better way to check equality when ArrayList contains null value             if(valueToCheck.equals(s)){                 tv.setText(tv.getText() + "\nWOW! " + valueToCheck + " found.");             }         }     } } 

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