Reading properties from a file with example
Reading
properties from file, find list of files in a directory and find a year is leap
year or not. These all example present in this post.
Read properties from file:
Reading properties from
properties(.properties) file is the major requirement in real-time applications.
Here, we will come to know, how to read properties from file with an example
explanation.
We will create
one .properties file with the name of javaex.properties under src package and
we will declare roleId's as key-value pairs. Like below,
application.id.roleIds = '53','121','63','46','43','71','45','36','64'
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Here,
application.id.roleIds is the Key to get the
values, which we will use in java class.
The below program explains you how to read data from the properties file by
using the key which you have declared in properties file.
package com.javatbrains.practice;
import
java.io.FileNotFoundException;
import java.io.InputStream;
import java.util.Properties;
public class CommaSeparated {
public static void main(String[] args) throws Exception {
try {
InputStream
stream = CommaSeparated.class.getClassLoader()
.getResourceAsStream("javaex.properties");
Properties
prop = new Properties();
prop.load(stream);
String
roleIds = prop.getProperty("application.id.roleIds");
String[]
roleId = roleIds.split(",");
for (int i = 0; i <= roleId.length - 1; i++) {
System.out.println("Role id is = " + roleId[i]);
}
} catch (FileNotFoundException e)
{
e.printStackTrace();
}
}
}
OutPut:
Role id is = '53'
Role id is = '121'
Role id is = '63'
Role id is = '46'
Role id is = '43'
Role id is = '71'
Role id is = '45'
Role id is = '36'
Role id is = '64'
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Steps:
• getClassLoader().getResourceAsStream()
method to loads the entire .properties file and stores into InputStream
• Create an object for Properties class, and loads input stream
instance into Properties class by using load method.
• By passing the .properties file key into getProperty method we will get matching value of passing key and assigned to String.
• Deviding the String value where all comma(,) is matching, and processing the results by using the for loop.
List of files in a directory:
Here is the one more real-time
scenario, like how to get list of file names in passing input directory. The
below example will explains you to how to get list of files and sub-directories
name in you C:\ drive. If you want to get some other
directory files list, you can change passing input directory to your directory.
Also it will print total no.of files in the console.
package com.javatbrains.practice;
import java.io.File;
public class ListOfFiles {
public static void main(String[] args) {
File f = null;
String[] paths;
try {
f = new File("C:/");
paths =
f.list();
for (String path : paths) {
System.out.println(f + "\\" + path);
}
System.out.println("Total no.of files : " + paths.length);
} catch (Exception e) {
e.printStackTrace();
}
}
}
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Steps:
• First
we need to create File object and passing input
directory into File("C:/") constructor only.
• list() method is used for getting
list of files in your passing input directory, and store into String[]
array.
• Finally
process the results by using the for loop and show all the files
path on console.
Find passing year is a leap year or not:
Finding an year is a leap year or not
is not a big challenge of the programmer in java. It is two steps process to
find an year is leap or not. Let us write a
program to test whether a given year is leap or not. The following logic used
for doing so:
• If year is
representing the beginning of a new century like 1900,2000 etc. It should be
divisible by 400. Then it is called leap year. To know whether the given year
is leap century year or not, we should divide it by 100. If it is divisible by
100, then it is a century year.
• If the year is not century year like 1998,2007,2010, etc. It
should be divisible by 4. Then it becomes leap year.
• If any of the above two cases are satisfied, then that year is
called leap year, otherwise it is not a leap year.
Here, is the program to find passing
year is leap or not.
package com.javatbrains.practice;
import java.io.BufferedReader;
import java.io.IOException;
import
java.io.InputStreamReader;
public class Leap {
public static void main(String[] args) throws NumberFormatException,
IOException {
// accept year
BufferedReader br
= new
BufferedReader(new InputStreamReader(System.in));
System.out.print("Enter year no: ");
int year = Integer.parseInt(br.readLine());
// If it is century year and divisible by 400
if (year % 100 == 0 || year
% 400 == 0) {
System.out.println("It is leap year");
// if it is not a century year and divisible by 4
} else if (year % 4 == 0 || year %
100 == 0) {
System.out.println("It is leap");
} else {
System.out.println("It is not leap");
}
}
}
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