io practice cases

3 practice cases

3.1 assemble to file [ application ]

  • Case requirements
    Read the data in the text file into the collection and traverse the collection. Requirement: each line of data in the file is a collection element

  • Implementation steps

    • Create character buffered input stream object
    • Create an ArrayList collection object
    • Call the method of character buffer input stream object to read data
    • Store the read string data in the collection
    • Release resources
    • Traversal set

  • code implementation

    public class TxtToArrayListDemo {
    public static void main(String[] args) throws IOException {
        //Create character buffered input stream object
        BufferedReader br = new BufferedReader(new FileReader("myCharStream\\array.txt"));

        //Create an ArrayList collection object
        ArrayList<String> array = new ArrayList<String>();

        //Call the method of character buffer input stream object to read data
        String line;
        while ((line=br.readLine())!=null) {
            //Store the read string data in the collection
            array.add(line);
        }
        //Release resources
        br.close();
        //Traversal set
        for(String s : array) {
            System.out.println(s);
        }
    }
}

3.2 file to collection [ application ]

  • Case requirements
    Write the string data in the ArrayList collection to a text file. Requirement: each string element is used as a line of data in the file

  • Implementation steps

    • Create an ArrayList collection
    • Storing string elements into a collection
    • Create character buffered output stream object
    • Traverse the collection to get each string data
    • Call the method of character buffered output stream object to write data
    • Release resources

  • code implementation

    public class ArrayListToTxtDemo {
    public static void main(String[] args) throws IOException {
        //Create an ArrayList collection
        ArrayList<String> array = new ArrayList<String>();

        //Storing string elements into a collection
        array.add("hello");
        array.add("world");
        array.add("java");

        //Create character buffered output stream object
        BufferedWriter bw = new BufferedWriter(new FileWriter("myCharStream\\array.txt"));

        //Traverse the collection to get each string data
        for(String s : array) {
            //Call the method of character buffer output stream object to write data
            bw.write(s);
            bw.newLine();
            bw.flush();
        }

        //Release resources
        bw.close();
    }
}

3.3 roll call device [ application ]

  • Case requirements
    I have a file that stores the names of the students in the class. Each name occupies one line. It is required to realize the random naming device through the program

  • Implementation steps

    • Create character buffered input stream object
    • Create an ArrayList collection object
    • Call the method of character buffered input stream object to read data
    • Store the read string data in the collection
    • Release resources
    • Use Random to generate a Random number. The range of Random numbers is: [0, the length of the set)
    • Use the random number generated in step 6 as an index to get the value in the ArrayList set
    • Output the data obtained in step 7 to the console

  • code implementation
    public class CallNameDemo {
    public static void main(String[] args) throws IOException {
    //Create character buffered input stream object
    BufferedReader br = new BufferedReader(new FileReader("myCharStream\names.txt"));

            //Create an ArrayList collection object
        ArrayList<String> array = new ArrayList<String>();

        //Call the method of character buffered input stream object to read data
        String line;
        while ((line=br.readLine())!=null) {
            //Store the read string data in the collection
            array.add(line);
        }

        //Release resources
        br.close();

        //Use Random to generate a Random number. The range of Random number is: [0, the length of the set)
        Random r = new Random();
        int index = r.nextInt(array.size());

        //Use the random number generated in step 6 as an index to get the value in the ArrayList set
        String name = array.get(index);

        //Output the data obtained in step 7 to the console
        System.out.println("The lucky ones are:" + name);
    }
}

3.4 collection to document improved version [ application ]

  • Case requirements
    Write the student data in the ArrayList collection to a text file. Requirements: the data of each student object is used as a line of data in the file
    Format: student number, name, age, residence example: itheima001, Lin Qingxia, 30, Xi'an
  • Implementation steps
    • Define student classes
    • Create an ArrayList collection
    • Create student object
    • Add student object to collection
    • Create character buffered output stream object
    • Traverse the collection to get each student object
    • Splice the data of the student object into a string in the specified format
    • Call the method of character buffered output stream object to write data
    • Release resources
  • code implementation

    • Student class

      public class Student {
    private String sid;
    private String name;
    private int age;
    private String address;

    public Student() {
    }

    public Student(String sid, String name, int age, String address) {
        this.sid = sid;
        this.name = name;
        this.age = age;
        this.address = address;
    }

    public String getSid() {
        return sid;
    }

    public void setSid(String sid) {
        this.sid = sid;
    }

    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }

    public int getAge() {
        return age;
    }

    public void setAge(int age) {
        this.age = age;
    }

    public String getAddress() {
        return address;
    }

    public void setAddress(String address) {
        this.address = address;
    }
}

    • Test class

      public class ArrayListToFileDemo {
    public static void main(String[] args) throws IOException {
        //Create an ArrayList collection
        ArrayList<Student> array = new ArrayList<Student>();

        //Create student object
        Student s1 = new Student("itheima001", "Lin Qingxia", 30, "Xi'an");
        Student s2 = new Student("itheima002", "Zhang Manyu", 35, "Wuhan");
        Student s3 = new Student("itheima003", "Wang Zuxian", 33, "Zhengzhou");

        //Add student object to collection
        array.add(s1);
        array.add(s2);
        array.add(s3);

        //Create character buffered output stream object
        BufferedWriter bw = new BufferedWriter(new FileWriter("myCharStream\\students.txt"));

        //Traverse the collection to get each student object
        for (Student s : array) {
            //Splice the data of the student object into a string in the specified format
            StringBuilder sb = new StringBuilder();
            sb.append(s.getSid()).append(",").append(s.getName()).append(",").append(s.getAge()).append(",").append(s.getAddress());

            //Call the method of character buffered output stream object to write data
            bw.write(sb.toString());
            bw.newLine();
            bw.flush();
        }

        //Release resources
        bw.close();
    }
}

3.5 document collection improved version [ application ]

  • Case requirements
    Read the data in the text file into the collection and traverse the collection. Requirements: each line of data in the file is the member variable value of a student object
    Example: itheima001, Lin Qingxia, 30, Xi'an
  • Implementation steps
    • Define student classes
    • Create character buffered input stream object
    • Create an ArrayList collection object
    • Call the method of character buffered input stream object to read data
    • Split the read string data with split() to get a string array
    • Create student object
    • Take out each element in the string array and assign the corresponding value to the member variable value of the student object
    • Add student object to collection
    • Release resources
    • Traversal set
  • code implementation

    • Student class
      ditto

    • Test class

      public class FileToArrayListDemo {
    public static void main(String[] args) throws IOException {
        //Create character buffered input stream object
        BufferedReader br = new BufferedReader(new FileReader("myCharStream\\students.txt"));

        //Create an ArrayList collection object
        ArrayList<Student> array = new ArrayList<Student>();

        //Call the method of character buffered input stream object to read data
        String line;
        while ((line = br.readLine()) != null) {
            //Split the read string data with split() to get a string array
            String[] strArray = line.split(",");

            //Create student object
            Student s = new Student();
            //Take out each element in the string array and assign the corresponding value to the member variable value of the student object
            //itheima001, Lin Qingxia, 30, Xi'an
            s.setSid(strArray[0]);
            s.setName(strArray[1]);
            s.setAge(Integer.parseInt(strArray[2]));
            s.setAddress(strArray[3]);

            //Add student object to collection
            array.add(s);
        }

        //Release resources
        br.close();

        //Traversal set
        for (Student s : array) {
            System.out.println(s.getSid() + "," + s.getName() + "," + s.getAge() + "," + s.getAddress());
        }
    }
}

Keywords: Java

Added by Albright on Wed, 19 Jan 2022 19:47:16 +0200

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