How do I use string in switch statement?

By I Wayan Saryada in Basic, Core API 0 Comment

Starting from Java 7 release you can now use a String in the switch statement. On the previous version we can only use constants type of byte, char, short, int (and their corresponding reference / wrapper type) or enum constants in the switch statement.

The code below give you a simple example on how the Java 7 extended to allow the use of String in switch statement.

package org.kodejava.basic;

public class StringInSwitchExample {
    public static void main(String[] args) {
        String day = "Sunday";
        switch (day) {
            case "Sunday":
                System.out.println("doSomething");
                break;
            case "Monday":
                System.out.println("doSomethingElse");
                break;
            case "Tuesday":
            case "Wednesday":
                System.out.println("doSomeOtherThings");
                break;
            default:
                System.out.println("doDefault");
                break;
        }
    }
}

How do I use multi-catch statement?

By I Wayan Saryada in Core API, Lang Package 1 Comment

The multi-catch is a language enhancement feature introduces in the Java 7. This allows us to use a single catch block to handle multiple exceptions. Each exception is separated by the pipe symbol (|).

Using the multi-catch simplify our exception handling and also reduce code duplicates in the catch block. Let’s see an example below:

package org.kodejava.lang;

import java.io.IOException;
import java.sql.SQLException;

public class MultiCatchDemo {
    public static void main(String[] args) {
        MultiCatchDemo demo = new MultiCatchDemo();
        try {
            demo.callA();
            demo.callB();
            demo.callC();
        } catch (IOException | SQLException | ClassNotFoundException e) {
            e.printStackTrace();
        }
    }

    private void callA() throws IOException {
        throw new IOException("IOException");
    }

    private void callB() throws SQLException {
        throw new SQLException("SQLException");
    }

    private void callC() throws ClassNotFoundException {
        throw new ClassNotFoundException("ClassNotFoundException");
    }
}

How do I read all lines from a file?

By I Wayan Saryada in Core API, IO 0 Comment

The java.nio.file.Files.readAllLines() method read all lines from a file. This method ensures that the file is closed when all bytes have been read or an I/O error, or other runtime exception, is thrown. Bytes from the file are decoded into characters using the specified charset.

Note that this method is intended for simple cases where it is convenient to read all lines in a single operation. It is not intended for reading in large files. This method is available since Java 7.

package org.kodejava.io;

import java.net.URI;
import java.nio.charset.Charset;
import java.nio.file.Files;
import java.nio.file.Paths;
import java.util.List;
import java.util.Objects;

public class ReadFileAsListDemo {
    public static void main(String[] args) {
        ReadFileAsListDemo demo = new ReadFileAsListDemo();
        demo.readFileAsList();
    }

    private void readFileAsList() {
        String fileName = "/data.txt";

        try {
            URI uri = Objects.requireNonNull(this.getClass().getResource(fileName)).toURI();
            List<String> lines = Files.readAllLines(Paths.get(uri),
                    Charset.defaultCharset());

            for (String line : lines) {
                System.out.println(line);
            }
        } catch (Exception e) {
            e.printStackTrace();
        }
    }
}

How do I count active thread in a thread group?

By I Wayan Saryada in Core API, Lang Package 0 Comment

This example describe how to get the number of active threads in this thread group. The result might not reflect concurrent activity, and might be affected by the presence of certain system threads.

Due to the inherently imprecise nature of the result, it is recommended that this method only be used for informational purposes.

package org.kodejava.lang;

public class ThreadGroupActiveThread {
    public static void main(String[] args) {
        ThreadGroup threadGroup = new ThreadGroup("TestThread");

        Thread t1 = new Thread(threadGroup, new Server(), "Server1");
        Thread t2 = new Thread(threadGroup, new Server(), "Server2");
        Thread t3 = new Thread(threadGroup, new Server(), "Server3");
        Thread t4 = new Thread(threadGroup, new Server(), "Server4");

        t1.start();
        t2.start();
        t3.start();
        t4.start();

        // Get an estimate number of active thread of the thread
        // group.
        int activeThread = threadGroup.activeCount();
        System.out.format("Number of active threads of %s is %d %n",
                threadGroup.getName(), activeThread);
    }
}

class Server implements Runnable {
    public void run() {
        System.out.println("Running..");
    }
}

How do I get number of active thread in current thread?

By I Wayan Saryada in Core API, Lang Package 0 Comment

In this example you’ll see how to obtain the number of active thread in the current thread. You can use the Thread.activeCount() method to get this information.

package org.kodejava.lang;

public class CountActiveThread {
    public static void main(String[] args) {
        Thread t = new Thread(() -> System.out.println("Hello..."));
        t.start();

        // Get the number of active threads in the current thread's
        // thread group.
        int activeThread = Thread.activeCount();
        System.out.format("Number of active threads of %s is %d %n",
                Thread.currentThread().getName(), activeThread);
    }
}