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 bar
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 Array
String[] redColors = new String[]{"Red", "Crimson", "Pink"};
// Initialize another Array
String[] blueColors = new String[]{"Blue", "AliceBlue"};
// Iterate over redColors array
tv.setText("Red colors : ");
for(int i=0;i<redColors.length;i++){
tv.setText(tv.getText() + redColors[i] + ", ");
}
// Iterate over blueColors array
tv.setText(tv.getText() + "\nBlue colors : ");
for(int i=0;i<blueColors.length;i++){
tv.setText(tv.getText() + blueColors[i] + ", ");
}
// Concatenate two arrays using custom method
String[] colors =concatenateTwoArrays(redColors, blueColors);
// Iterate over redColors array
tv.setText(tv.getText() + "\n\nAll colors : ");
for(int i=0;i<colors.length;i++){
tv.setText(tv.getText() + colors[i] + ", ");
}
// Initialize an Integer array
Integer[] numbers = new Integer[]{1,2,3,4};
// Iterate over numbers array
tv.setText(tv.getText() + "\n\nNumbers : ");
for(int i=0;i<numbers.length;i++){
tv.setText(tv.getText() + "" + numbers[i] + ", ");
}
// Initialize another Integer array
Integer[] numbersTenUp = new Integer[]{11,12,13};
// Iterate over numbersTenUp array
tv.setText(tv.getText() + "\nNumbers ten up : ");
for(int i=0;i<numbersTenUp.length;i++){
tv.setText(tv.getText() + "" + numbersTenUp[i] + ", ");
}
// Initialize another Integer array
Integer[] numbersFiftyUp = new Integer[]{51,55};
// Iterate over numbersFiftyUp array
tv.setText(tv.getText() + "\nNumbers fifty up : ");
for(int i=0;i<numbersFiftyUp.length;i++){
tv.setText(tv.getText() + "" + numbersFiftyUp[i] + ", ");
}
// Initialize an ArrayList
List<Integer> allNumbers = new ArrayList<>();
// Add numbers array elements to list
Collections.addAll(allNumbers,numbers);
// Add numbersTenUp array elements to list
Collections.addAll(allNumbers,numbersTenUp);
// Add numbersFiftyUp array elements to list
Collections.addAll(allNumbers,numbersFiftyUp);
// Concatenate all the three Integer arrays
// This is the way to concatenate multiple arrays
Integer[] result = allNumbers.toArray(new Integer[allNumbers.size()]);
// Iterate over concatenated Integer arrays
tv.setText(tv.getText() + "\n\nAll numbers : ");
for(int i=0;i<result.length;i++){
tv.setText(tv.getText() + "" + result[i] + ", ");
}
}
// Custom method to concatenate two String arrays
protected String[] concatenateTwoArrays(String[] arrayFirst,String[] arraySecond){
// Initialize an empty list
List<String> both = new ArrayList<>();
// Add first array elements to list
Collections.addAll(both,arrayFirst);
// Add another array elements to list
Collections.addAll(both,arraySecond);
// Convert list to array
String[] result = both.toArray(new String[both.size()]);
// Return the result
return result;
}
}

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