Java Programming and more

Friday, December 30, 2016

How to Add Back Button in Android

@Override

protected void onCreate(Bundle savedInstanceState) {

super.onCreate(savedInstanceState);

setContentView(R.layout.activity_loan_list);

getSupportActionBar().setDisplayHomeAsUpEnabled(true);

}

@Override

public boolean onOptionsItemSelected(MenuItem item) {

// Handle action bar item clicks here. The action bar will

// automatically handle clicks on the Home/Up button, so long

// as you specify a parent activity in AndroidManifest.xml.

int id = item.getItemId();

switch (id){

case android.R.id.home:

onBackPressed();

break;

default:

break;

}

return super.onOptionsItemSelected(item);

}

Monday, January 12, 2015

Recursion Problem in Java: Reverse a sentence

Problem: Write a recursive function to reverse the words in a string, i.e., "cat is running"
becomes "running is cat".

public String reverse(String str, int ctr){
if(str.lastIndexOf(" ")==-1) return str;
return str.substring(str.lastIndexOf(" ")+1) + " " +

        reverse(str.substring(0, str.lastIndexOf(" ")),ctr+1);
    }

Recursion Problem in Java: Reverse a word

Problem: Write a recursive function to reverse a string.
Ex. "programmer" becomes "remmargorp"


    public String reverse(String str){

    if(str.length()==0) return "";

    return str.substring(str.length()-1) + reverse(str.substring(0, str.length()-1));

    }

Saturday, December 27, 2014

How to Generate Random Colors in Java

This is the code I used to generate random colors in JPanel. You can adjust the values for hue & saturation to get the color you want.

Don't forget to import java.awt.Color & java.util.Random

public Color generateColor(){
Color color;
Random random = new Random();
//to get rainbow, pastel colors
final float hue = random.nextFloat();
final float saturation = 1.0f; //1.0 for brilliant, 0.0 for dull
final float luminance = 0.6f; //1.0 for brighter, 0.0 for black
color = Color.getHSBColor(hue, saturation, luminance);
return color;
}

Usage: MyPanel.setBackground(generateColor());

Thursday, December 25, 2014

Writing an HTML file from a template using Java

Create a template and save as template.html .

<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN""http://www.w3.org/TR/html4/loose.dtd"><html><head><meta http-equiv="Content-Type" content="text/html; charset=UTF-8"><title>[TITLE]</title></head><body>[BODY]</body></html>

Put a tag like [TAG] for any dynamic content and then do something like this:

File htmlTemplateFile = new File("path/template.html");String htmlString = FileUtils.readFileToString(htmlTemplateFile);String title = "New Page";String body = "This is Body";htmlString = htmlString.replace("[TITLE]", title);htmlString = htmlString.replace("[BODY]", body);File newHtmlFile = new File("path/new.html");FileUtils.writeStringToFile(newHtmlFile, htmlString);

Note: You will need to import org.apache.commons.io.FileUtils to do this.