Linggo, Abril 1, 2018

How to make a simple input and output statement in java

How to make I/O Statement in Java

No matter which programming language one chooses, performing input and output operations are the core knowledge that one definitely needs to posses. From disk files, devices, other programs to memory arrays, a stream can represent a variety of data sources and destinations. This article will teach you how to use the four most important input and output streams in Java.

Method One of Four:
Using Byte and Character Streams

Byte streams handle input and output of raw binary data, byte by byte. Raw binary data is the type of data that hasn't been processed yet, bunch of ones and zeroes.

Character streams handle and translate input and output of character data, character by character. Translation, in this case, means that character streams automatically transform character format from and to the local character set.
  1. 1
    Create a text file. Give it an arbitrary name and write something in it, such as I love wikiHow!. In this article, we will name it file.txt.
  2. 2
    Create a main method. You can add throws IOException declaration to the method signature to avoid adding the catch block to the try-with-resources block.
    public static void main(String[] args) {
 
}
  3. 3
    Create a try-with-resources block.Try-with-resources block will automatically close streams for us.
    public static void main(String[] args) {
  try () {
 
  }
}
  4. 4
    Create FileInputStream or FileReaderin the block statement. In the constructor of the created input stream, specify the name of the text file previously created. In this article, we called it file.txt.
    public static void main(String[] args) {
  try (FileInputStream in = new FileInputStream("file.txt")) {
 
  }
}
    • The former is a byte stream, the latter is a character stream.
  5. 5
    Create FileOutputStream or FileWriterin the block statement. In the constructor of the created output stream, specify another arbitrary text file name. In this article, we will name it file-copy.txt.
    public static void main(String[] args) {
  try (
      FileInputStream in = new FileInputStream("file.txt");
      FileOutputStream out = new FileOutputStream("file-copy.txt")
  ) {
 
  }
}
    • If you created FileInputStream, you need to create FileOutputStream. The same goes for the FileReader and FileWriter.
    • 6
      Create int variable. This variable will be used for temporary storage of read byte or character.
      public static void main(String[] args) {
  try (
      FileInputStream in = new FileInputStream("file.txt");
      FileOutputStream out = new FileOutputStream("file-copy.txt")
  ) {
    int data;
  }
}
    • 7
      Read data from input stream. Create a while loop in which the data is read into the previously created int variable until it reads the number -1. In other words, it reads data from the file until it reaches the end of the file.
      public static void main(String[] args) {
  try (
      FileInputStream in = new FileInputStream("file.txt");
      FileOutputStream out = new FileOutputStream("file-copy.txt")
  ) {
    int data;
    while ((data = in.read()) != -1) {
 
    }
  }
}
    • 8
      Write data to the output stream. In the body of the while loop, write the read data to the output stream.
      public static void main(String[] args) {
  try (
      FileInputStream in = new FileInputStream("file.txt");
      FileOutputStream out = new FileOutputStream("file-copy.txt")
  ) {
    int data;
    while ((data = in.read()) != -1) {
      out.write(data);
    }
  }
}
    • 9
      Catch and handle IOException. Add a catch block to the try-with-resources block, catch IOException and, in case of an error, print the stack trace to the console.
      public static void main(String[] args) {
  try (
      FileInputStream in = new FileInputStream("file.txt");
      FileOutputStream out = new FileOutputStream("file-copy.txt")
  ) {
    int data;
    while ((data = in.read()) != -1) {
      out.write(data);
    }
  } catch (IOException e) {
    e.printStackTrace();
  }
}
    • 10
      Run the program. Contents of the file.txt are copied to the file-copy.txtwhich, if it doesn't exist yet, is created

      1. Method Two of Four:
        Using Buffered Streams

        Buffered streams optimize input and output data. Buffer streams are more efficient than byte and character streams as they read and write from a buffer that is handled by Java platform rather than the underlying operating system. Most common usage of buffered streams is reading a textual file, line by line.
        1. 1
          Create a text file. Give it an arbitrary name and write something in it, such as I love wikiHow!. In this article, we will name it file.txt.
        2. 2
          Create a main method. You can add throws IOException declaration to the method signature to avoid adding the catch block to the try-with-resources block.
          public static void main(String[] args) {
 
}
        3. 3
          Create a try-with-resources block.Try-with-resources block will automatically close streams for us.
          public static void main(String[] args) {
  try () {
 
  }
}
        4. 4
          Create BufferedReader in the block statement. In the constructor of the created input stream, create a FileReaderand specify the name of the text file previously created inside its constructor. In this article, we called it file.txt.
          public static void main(String[] args) {
  try (BufferedReader in = new BufferedReader(new FileReader("file.txt"))) {
 
  }
}
        5. 5
          Create BufferedWriter in the block statement. In the constructor of the created output stream, create a FileWriterand specify another arbitrary text file name in its constructor. In this article, we will name it file-copy.txt.
          public static void main(String[] args) {
  try (
      BufferedReader in = new BufferedReader(new FileReader("file.txt"));
      BufferedWriter out = new BufferedWriter(new FileWriter("file-copy.txt"))
  ) {
 
  }
}
        6. 6
          Create String variable. This variable will be used for temporary storage of read lines.
          public static void main(String[] args) {
  try (
      BufferedReader in = new BufferedReader(new FileReader("file.txt"));
      BufferedWriter out = new BufferedWriter(new FileWriter("file-copy.txt"))
  ) {
    String line;
  }
}
        7. 7
          Read lines from input stream. Create a while loop in which the lines are read into the previously created String variable until it reads null. In other words, it reads data from the file until it reaches the end of the file.
          public static void main(String[] args) {
  try (
      BufferedReader in = new BufferedReader(new FileReader("file.txt"));
      BufferedWriter out = new BufferedWriter(new FileWriter("file-copy.txt"))
  ) {
    String line;
    while ((line = in.readLine()) != null) {
 
    }
  }
}
        8. 8
          Write lines to the output stream with line separator. In the body of the while loop, write the read lines to the output stream and append the line separator at the end of each line. BufferedReader reads lines, but omits the line separator.
          public static void main(String[] args) {
  try (
      BufferedReader in = new BufferedReader(new FileReader("file.txt"));
      BufferedWriter out = new BufferedWriter(new FileWriter("file-copy.txt"))
  ) {
    String line;
    while ((line = in.readLine()) != null) {
      out.write(line + System.lineSeparator());
    }
  }
}
        9. 9
          Catch and handle IOException. Add a catch block to the try-with-resources block, catch IOException and, in case of an error, print the stack trace to the console.
          public static void main(String[] args) {
  try (
      BufferedReader in = new BufferedReader(new FileReader("file.txt"));
      BufferedWriter out = new BufferedWriter(new FileWriter("file-copy.txt"))
  ) {
    String line;
    while ((line = in.readLine()) != null) {
      out.write(line + System.lineSeparator());
    }
  } catch (IOException e) {
    e.printStackTrace();
  }
}
        10. 10
          Run the program. Contents of the file.txt are copied to the file-copy.txtwhich, if it doesn't exist yet, is created.

        11. Method Three of Four:
          Using Data Streams

          Data streams handle binary input and output of primitive data types and Strings. Data streams make it very easy to read and write boolean, char, byte, short, int, long, float, double and String values. Most common usage of data streams is in network applications (e.g. instant messengers).
          1. 1
            Create a main method. You can add throws IOException declaration to the method signature to avoid adding the catch block to the try-with-resources block.
            public static void main(String[] args) {
 
}
          2. 2
            Create a try-with-resources block.Try-with-resources block will automatically close streams for us.
            public static void main(String[] args) {
  try () {
 
  }
}
          3. 3
            Create DataOutputStream in the block statement. In the constructor of the created input stream, create FileOutputStream and specify an arbitrary file name inside its constructor. In this article, we will name it file.txt.
            public static void main(String[] args) {
  try (DataOutputStream out = new DataOutputStream(new FileOutputStream("file.txt"))) {
 
  }
}
          4. 4
            Create DataInputStream in the block statement. In the constructor of the created input stream, create a FileInputStream and specify file name from the previous step inside its constructor. In this article, we named it file.txt.
            public static void main(String[] args) {
  try (
      DataOutputStream out = new DataOutputStream(new FileOutputStream("file.txt"));
      DataInputStream in = new DataInputStream(new FileInputStream("file.txt"))
  ) {
 
  }
}
          5. 5
            Write some data to the output stream.In the body of the try-with-resources block, write String, boolean, int and other primitive data to the output stream.
            public static void main(String[] args) {
  try (
      DataOutputStream out = new DataOutputStream(new FileOutputStream("file.txt"));
      DataInputStream in = new DataInputStream(new FileInputStream("file.txt"))
  ) {
    out.writeUTF("wikiHow is a great place to learn");
    out.writeBoolean(true);
    out.writeInt(10430);
    out.writeDouble(20.9d);
    out.writeFloat(23.10f);
  }
}
          6. 6
            Read data from the input stream and print it. Read the data in the same order as it has been written and print it to the console.
            public static void main(String[] args) {
  try (
      DataOutputStream out = new DataOutputStream(new FileOutputStream("file.txt"));
      DataInputStream in = new DataInputStream(new FileInputStream("file.txt"))
  ) {
    out.writeUTF("wikiHow is a great place to learn");
    out.writeBoolean(true);
    out.writeInt(10430);
    out.writeDouble(20.9d);
    out.writeFloat(23.10f);
 
    System.out.println(in.readUTF());
    System.out.println(in.readBoolean());
    System.out.println(in.readInt());
    System.out.println(in.readDouble());
    System.out.println(in.readFloat());
  }
}
          7. 7
            Catch and handle IOException. Add a catch block to the try-with-resources block, catch IOException and, in case of an error, print the stack trace to the console.
            public static void main(String[] args) {
  try (
      DataOutputStream out = new DataOutputStream(new FileOutputStream("file.txt"));
      DataInputStream in = new DataInputStream(new FileInputStream("file.txt"))
  ) {
    out.writeUTF("wikiHow is a great place to learn");
    out.writeBoolean(true);
    out.writeInt(10430);
    out.writeDouble(20.9d);
    out.writeFloat(23.10f);
 
    System.out.println(in.readUTF());
    System.out.println(in.readBoolean());
    System.out.println(in.readInt());
    System.out.println(in.readDouble());
    System.out.println(in.readFloat());
  } catch (IOException e) {
    e.printStackTrace();
  }
}
          8. 8
            Run the program. Data is written to the file.txt and then read and printed to the console.
            wikiHow is a great place to learn
true
10430
20.9
23.1
          9. 
Method Four of Four:
Using Object Streams
            

            

            
Object streams handle binary input and output of Java objects. Like data streams, object streams make it very easy to read and write primitive data types and Strings, but also any object that implements Serializableinterface. Most common usage of object streams is in network applications where both server and client are written in Java.
            

              

            1. 
1
              

              
Create a serializable class. Create a class that implements Serializableinterface. Name the class however you'd like, but in this article we will name it WikiHowian.
              

              

              

              public class WikiHowian implements Serializable {
 
}

              

              

              

              

              

              

              

              2. 

            2. 
2
              

              
Create a few private (serializable) variables. Since WikiHowian class represents a person, we will create two String variables for first and last name and an int variable for age.
              

              

              

              public class WikiHowian implements Serializable {
  private String firstName, lastName;
  private int age;
}

              

              

              

              

              

              

              

              3. 

            3. 
3
              

              
Create a constructor. The constructor will contain firstName, secondNameand age parameters, corresponding to the private variable types.
              

              

              

              public class WikiHowian implements Serializable {
  private String firstName, lastName;
  private int age;
 
  public WikiHowian(String firstName, String lastName, int age) {
    this.firstName = firstName;
    this.lastName = lastName;
    this.age = age;
  }
}

              

              

              

              

              

              

              

              4. 

            4. 
4
              

              
Override toString method. Overriding toString will, later on, allow us to print the object to the console easily.
              

              

              

              public class WikiHowian implements Serializable {
  private String firstName, lastName;
  private int age;
 
  public WikiHowian(String firstName, String lastName, int age) {
    this.firstName = firstName;
    this.lastName = lastName;
    this.age = age;
  }
 
  @Override
  public String toString() {
    return firstName + " " + lastName + ", " + age;
  }
}

              

              

              

              

              

              

              

              5. 

            5. 
5
              

              
Create a main method. You can add throws IOException, ClassNotFoundException declaration to the method signature to avoid adding the catch block to the try-with-resources block.
              

              

              

              public class WikiHowian implements Serializable {
  private String firstName, lastName;
  private int age;
 
  public WikiHowian(String firstName, String lastName, int age) {
    this.firstName = firstName;
    this.lastName = lastName;
    this.age = age;
  }
 
  @Override
  public String toString() {
    return firstName + " " + lastName + ", " + age;
  }
 
  public static void main(String[] args) {
 
  }
}

              

              

              

              

              

              

              

              6. 

            6. 
6
              

              
Create a try-with-resources block.Try-with-resources block will automatically close streams for us.
              

              

              

              public class WikiHowian implements Serializable {
 
  private String firstName, lastName;
  private int age;
 
  public WikiHowian(String firstName, String lastName, int age) {
    this.firstName = firstName;
    this.lastName = lastName;
    this.age = age;
  }
 
  @Override
  public String toString() {
    return firstName + " " + lastName + ", " + age;
  }
 
  public static void main(String[] args) {
    try () {
 
    }
  }
}

              

              

              

              

              

              

              

              7. 

            7. 
7
              

              
Create ObjectOutputStream in the block statement. In the constructor of the created input stream, create FileOutputStream and specify an arbitrary file name inside its constructor. In this article, we will name it file.txt.
              

              

              

              public class WikiHowian implements Serializable {
 
  private String firstName, lastName;
  private int age;
 
  public WikiHowian(String firstName, String lastName, int age) {
    this.firstName = firstName;
    this.lastName = lastName;
    this.age = age;
  }
 
  @Override
  public String toString() {
    return firstName + " " + lastName + ", " + age;
  }
 
  public static void main(String[] args) {
    try (ObjectOutputStream out = new ObjectOutputStream(new FileOutputStream("file.txt"))) {
 
    }
  }
}

              

              

              

              

              

              

              

              8. 

            8. 
8
              

              
Create ObjectInputStream in the block statement. In the constructor of the created input stream, create a FileInputStream and specify file name from the previous step inside its constructor. In this article, we named it file.txt.
              

              

              

              public class WikiHowian implements Serializable {
 
  private String firstName, lastName;
  private int age;
 
  public WikiHowian(String firstName, String lastName, int age) {
    this.firstName = firstName;
    this.lastName = lastName;
    this.age = age;
  }
 
  @Override
  public String toString() {
    return firstName + " " + lastName + ", " + age;
  }
 
  public static void main(String[] args) {
    try (
        ObjectOutputStream out = new ObjectOutputStream(new FileOutputStream("file.txt"));
        ObjectInputStream in = new ObjectInputStream(new FileInputStream("file.txt"))
    ) {
    }
  }
}

              

              

              

              

              

              

              

              9. 

            9. 
9
              

              
Instantiate the previously created serializable class. Choose first name, last name and age arbitrarily.
              

              

              

              public class WikiHowian implements Serializable {
 
  private String firstName, lastName;
  private int age;
 
  public WikiHowian(String firstName, String lastName, int age) {
    this.firstName = firstName;
    this.lastName = lastName;
    this.age = age;
  }
 
  @Override
  public String toString() {
    return firstName + " " + lastName + ", " + age;
  }
 
  public static void main(String[] args) {
    try (
        ObjectOutputStream out = new ObjectOutputStream(new FileOutputStream("file.txt"));
        ObjectInputStream in = new ObjectInputStream(new FileInputStream("file.txt"))
    ) {
      WikiHowian wikiHowian = new WikiHowian("John", "Doe", 23);
    }
  }
}

              

              

              

              

              

              

              

              10. 

            10. 
10
              

              
Write object to the output stream.Exactly, you can write the complete object to the output stream. The object, as it implements Serializable interface, is serialized into ones and zeroes, and stored in the file.
              

              

              

              public class WikiHowian implements Serializable {
 
  private String firstName, lastName;
  private int age;
 
  public WikiHowian(String firstName, String lastName, int age) {
    this.firstName = firstName;
    this.lastName = lastName;
    this.age = age;
  }
 
  @Override
  public String toString() {
    return firstName + " " + lastName + ", " + age;
  }
 
  public static void main(String[] args) {
    try (
        ObjectOutputStream out = new ObjectOutputStream(new FileOutputStream("file.txt"));
        ObjectInputStream in = new ObjectInputStream(new FileInputStream("file.txt"))
    ) {
      WikiHowian wikiHowian = new WikiHowian("John", "Doe", 23);
      out.writeObject(wikiHowian);
    }
  }
}

              

              

              

              

              

              

              

              11. 

            11. 
11
              

              
Read object from the input stream and print it. Same way the object was written to a file, we read it from the file and, thanks to overriding toString method, easily print it to the console.
              

              

              

              public class WikiHowian implements Serializable {
 
  private String firstName, lastName;
  private int age;
 
  public WikiHowian(String firstName, String lastName, int age) {
    this.firstName = firstName;
    this.lastName = lastName;
    this.age = age;
  }
 
  @Override
  public String toString() {
    return firstName + " " + lastName + ", " + age;
  }
 
  public static void main(String[] args) {
    try (
        ObjectOutputStream out = new ObjectOutputStream(new FileOutputStream("file.txt"));
        ObjectInputStream in = new ObjectInputStream(new FileInputStream("file.txt"))
    ) {
      WikiHowian wikiHowian = new WikiHowian("John", "Doe", 23);
      out.writeObject(wikiHowian);
      System.out.println(in.readObject());
    }
  }
}

              

              

              

              

              

              

              

              12. 

            12. 
12
              

              
Catch and handle IOException and ClassNotFoundException. Add a catch block to the try-with-resources block, catch IOException and ClassNotFoundException. In case of an error, print the stack trace to the console.
              

              

              

              public class WikiHowian implements Serializable {
 
  private String firstName, lastName;
  private int age;
 
  public WikiHowian(String firstName, String lastName, int age) {
    this.firstName = firstName;
    this.lastName = lastName;
    this.age = age;
  }
 
  @Override
  public String toString() {
    return firstName + " " + lastName + ", " + age;
  }
 
  public static void main(String[] args) {
    try (
        ObjectOutputStream out = new ObjectOutputStream(new FileOutputStream("file.txt"));
        ObjectInputStream in = new ObjectInputStream(new FileInputStream("file.txt"))
    ) {
      WikiHowian wikiHowian = new WikiHowian("John", "Doe", 23);
      out.writeObject(wikiHowian);
      System.out.println(in.readObject());
    } catch (IOException | ClassNotFoundException e) {
      e.printStackTrace();
    }
  }
}

              

              

              

              

              

              

              

              13. 

            13. 
13
              

              
Run the program. Object is transformed (serialized) into ones and zeroes, and written to a file. Afterwards, ones and zeroes are read and constructed back into an object.
              

              

              

              John Doe, 23
              

              

              

              

              

              14.
Ipinaskil ni sa

2 komento:

  1. UnknownAbril 3, 2018 nang 2:25 AM

    thanks for the info. Where did you learn programming in java?

    TumugonBurahin
    Mga Tugon
    1. UnknownAbril 3, 2018 nang 3:49 AM

      I just learned in school with you haha. By the way programming is fun and has logic.

      Burahin

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