java - How to sort 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.Collections; import java.util.List;   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 kafe         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("Crimson");         colors.add("Green");         colors.add("Yellow");         colors.add("Aqua");         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) + ", ");         }          // Sort the ArrayList         // Sort ArrayList elements in ascending order         Collections.sort(colors);          // Iterate through colors ArrayList         tv.setText(tv.getText() + "\nSorted colors : ");         for(int i=0;i<colors.size();i++){             tv.setText(tv.getText() + colors.get(i) + ", ");         }          // Initialize a new ArrayList         List<String> animals = new ArrayList<>();         animals.add("Bison");         animals.add("Tiger");         animals.add("Zebra");         animals.add("Cat");          // Iterate through animals ArrayList         tv.setText(tv.getText() + "\n\nAnimals : ");         for(int i=0;i<animals.size();i++){             tv.setText(tv.getText() + animals.get(i) + ", ");         }          /*             Simple technique to sort an ArrayList in descending order             At first sort it ascending order             Then reverse the ArrayList elements order             Finally, You get ArrayList elements sorted in descending order         */         // Sort the ArrayList         Collections.sort(animals);         // Reverse the ArrayList elements order         Collections.reverse(animals);          // Iterate through descending sorted animals ArrayList         tv.setText(tv.getText() + "\nDescending sorted animals : ");         for(int i=0;i<animals.size();i++){             tv.setText(tv.getText() + animals.get(i) + ", ");         }     } }
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