Reading Properties files in JAVA

Before jumping into reading properties file, let’s first create a project as below:

Now let’s put some values inside this object.properties.

name=Deepak
job= Software Engineer
age=30

Now let’s create another package where we will call this properties file

package test;

import java.io.FileInputStream;
import java.io.FileNotFoundException;
import java.io.IOException;
import java.util.Properties;

public class TestCase1 {

	
	public static void main(String[] args) throws IOException {
		
		Properties prop = new Properties(); // Creating instance of properties class of Java
		FileInputStream fis = new FileInputStream(System.getProperty("user.dir")+"/src/config/object.properties");
		
		prop.load(fis);
		
		System.out.println(prop.getProperty("name"));
		System.out.println(prop.getProperty("job"));
		
	}
}

Java Stream

Java streams are used to write/read from a file.

Below code shows how to write to a .txt file

package test;

import java.io.BufferedWriter;
import java.io.File;
import java.io.FileWriter;
import java.io.IOException;

public class TestCase2 {
	
	public static void main(String[] args) throws IOException {
		
		File f = new File(System.getProperty("user.dir")+"/myTextFile.txt");
		FileWriter fw = new FileWriter(f,false);
		BufferedWriter writer = new BufferedWriter(fw);
		
		for (int i = 0; i < 4; i++) {
			for (int j = 0; j < 3; j++) {
				
				int num = (int)(Math.random()*100);
				writer.write(num+"\t");//use a , to write to csv
			}
			writer.newLine();
		}
		
		writer.close();
	}

}

Below code shows how to read from file

package test;

import java.io.BufferedReader;
import java.io.File;
import java.io.FileReader;
import java.io.IOException;

public class TestCase3 {

public static void main(String[] args) throws IOException {
		
		File f = new File(System.getProperty("user.dir")+"/myTextFile.txt");
		FileReader fw = new FileReader(f);
		BufferedReader reader = new BufferedReader(fw);
		
		//System.out.println(reader.readLine());
		
		String line = null;
		//if above line of code is not written then it will skip the first line
		while((line=reader.readLine())!=null) {
			System.out.println(line);
		}
		
		reader.close();
	}
}

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