java - How to remove a key from HashMap while iterating

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.HashMap; import java.util.Map; 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 HashMap         Map<Integer,String> colors = new HashMap<>();         // Put some entry to the map         colors.put(1,"Red");         colors.put(2,"Green");         colors.put(3,"Blue");         colors.put(4,"Black");         colors.put(5,"Yellow");          // Iterate over HashMap and remove an entry which value is 'Blue'         tv.setText("Colors : ");         Iterator it = colors.entrySet().iterator();         while(it.hasNext()){             Map.Entry pair = (Map.Entry) it.next();             tv.setText(tv.getText() + "\n" + pair.getKey() +  " : " + pair.getValue());             if(pair.getValue().equals("Blue")){                 it.remove();             }         }          // Iterate over HashMap after removing a pair         tv.setText(tv.getText() + "\n\nColors (after removing 'Blue'): ");         Iterator itr = colors.entrySet().iterator();         while(itr.hasNext()){             Map.Entry pair = (Map.Entry) itr.next();             tv.setText(tv.getText() + "\n" + pair.getKey() + " : " + pair.getValue());         }          // Another way to remove a pair from HashMap while iterating         // For loop to remove an entry from HashMap         for(Iterator<Map.Entry<Integer,String>> ite = colors.entrySet().iterator(); ite.hasNext();)         {             Map.Entry<Integer,String> pair = ite.next();             if(pair.getKey()==2){                 // If key == 2 the remove the pair from HashMap                 ite.remove();             }         }          // Iterate over HashMap after removing an entry         tv.setText(tv.getText() + "\n\nColors (after removing key '2'): ");         Iterator iterator = colors.entrySet().iterator();         while(iterator.hasNext()){             Map.Entry pair = (Map.Entry) iterator.next();             tv.setText(tv.getText() + "\n" + pair.getKey() + " : " + pair.getValue());         }    } }
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