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3. file
3.1 Exercise.java
import java.io.File;
import java.io.FileNotFoundException;
import java.util.ArrayList;
import java.util.Collections;
import java.util.List;
import java.util.Scanner;
public class Exercise {
public static void main(String[] args) {
//exercise2();
}
public static void exercise1() {
String pathToFile = "C:\\Users\\thieu.bui\\Downloads\\dataset_91033.txt";
File file = new File(pathToFile);
int sum = 0;
try (Scanner scanner2 = new Scanner(file)) {
while (scanner2.hasNextInt()) {
sum += scanner2.nextInt();
}
} catch (FileNotFoundException e) {
System.out.println("No file found: " + pathToFile);
}
System.out.println(sum);
}
public static void exercise2() {
String pathToFile = "C:\\Users\\thieu.bui\\Downloads\\dataset_91007.txt";
File file = new File(pathToFile);
int greatest = 0;
int num;
try (Scanner scanner2 = new Scanner(file)) {
while (scanner2.hasNextInt()) {
num = scanner2.nextInt();
if (num > greatest) {
greatest = num;
}
}
} catch (FileNotFoundException e) {
System.out.println("No file found: " + pathToFile);
}
System.out.println(greatest);
}
int process(int a, int b) {
return 0;
}
public List<File> getAllFiles(File rootDir) {
File[] children = rootDir.listFiles();
if (children == null || children.length == 0) {
return Collections.emptyList();
}
List<File> files = new ArrayList<>();
for (File child : children) {
if (child.isDirectory()) {
files.addAll(getAllFiles(child));
} else {
files.add(child);
}
}
return files;
}
}
################################
3.2. FileClass.java
import java.io.File;
/*
Objects of the File class are immutable
*/
public class FileClass {
public static void main(String[] args) {
System.out.println(File.separator);
basicMethod();
}
public static void path() {
File absolutePath = new File("D:\\Materials\\java-materials.pdf");
File relativePath = new File(".\\images\\picture.jpg");
}
public static void basicMethod() {
File file = new File(".\\Learning\\Java\\LearningJava\\TestFile.txt");
System.out.println("File name: " + file.getName());
System.out.println("File path: " + file.getPath());
System.out.println("Is file: " + file.isFile());
System.out.println("Is directory: " + file.isDirectory());
System.out.println("Exists: " + file.exists());
System.out.println("Parent path: " + file.getParent());
}
}
##########################################
3.3. ReadingFile.java
import java.io.File;
import java.io.FileNotFoundException;
import java.io.IOException;
import java.nio.file.Files;
import java.nio.file.Paths;
import java.util.Scanner;
public class ReadingFile {
public static void main(String[] args) {
//usingScanner();
String pathToFile = "D:\\Learning\\Java\\LearningJava\\TestFile.txt";
try {
System.out.println(Files.readAllLines(Paths.get(pathToFile)));
} catch (IOException e) {
System.out.println("Cannot read file: " + e.getMessage());
}
}
public static void usingScanner() {
String pathToFile = "D:\\Learning\\Java\\LearningJava\\TestFile.txt";
File file = new File(pathToFile);
// Scanner scanner1 = new Scanner(file); // it throws FileNotFoundException (checked)
try (Scanner scanner2 = new Scanner(file)) {
while (scanner2.hasNext()) {
System.out.print(scanner2.nextLine() + " ");
}
} catch (FileNotFoundException e) {
System.out.println("No file found: " + pathToFile);
}
}
public static String readFileAsString(String fileName) throws IOException {
return new String(Files.readAllBytes(Paths.get(fileName)));
}
}
#######################################
3.4. WritingFile.java
import java.io.File;
import java.io.FileWriter;
import java.io.IOException;
import java.io.PrintWriter;
public class WritingFile {
public static void main(String[] args) {
fileWriter();
}
/*
FileWriter(String fileName);
FileWriter(String fileName, boolean append);
FileWriter(File file);
FileWriter(File file, boolean append);
*/
public static void fileWriter() {
File file = new File("D:\\Learning\\Java\\LearningJava\\file.txt");
try(FileWriter writer = new FileWriter(file)) { // overwrites the file
writer.write("Hello ");
writer.write("Java");
} catch (IOException e) {
System.out.println(e.getMessage());
}
// writer.close() -> tranh memory leak
}
/*
PrintWriter(String fileName);
PrintWriter(File file);
PrintWriter(Writer writer).
*/
public static void printWriter() {
File file = new File("D:\\Learning\\Java\\LearningJava\\file.txt");
try (PrintWriter printWriter = new PrintWriter(file)) {
printWriter.print("Hello"); // prints a string
printWriter.println("Java"); // prints a string and then terminates the line
printWriter.println(123); // prints a number
printWriter.printf("You have %d %s", 400, "gold coins"); // prints a formatted string
} catch (IOException e) {
System.out.printf("An exception occurred %s", e.getMessage());
}
}
}
#########################################
4. iostream
4.1. outputstream
4.2. inputstream
4.2.1. Exercise.java
import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;
public class Exercise {
public static void main(String[] args) throws Exception {
readSequenceOfBytes();
}
public static void test1() throws IOException {
BufferedReader reader = new BufferedReader(new InputStreamReader(System.in));
// start coding here
char[] arr = new char[50];
int number = reader.read(arr);
for (int i = number - 1; i >= 0; i--) {
System.out.print(arr[i]);
}
reader.close();
}
public static void readSequenceOfBytes() throws IOException {
// input: abc
// output: 979899
InputStream inputStream = System.in;
byte[] bytes = new byte[1024];
int numberOfBytes = inputStream.read(bytes);
for (int i = 0; i < numberOfBytes; i++) {
System.out.print(bytes[i]);
}
}
}
####################################
4.2.2. Main.java
import java.io.*;
import java.util.Arrays;
public class Main {
public static void main(String[] args) {
characterStream();
byteStream();
}
/*
Co nhieu class cho viec doc text -> character input streams: char va string
vi du: FileReader, CharArrayReader, StringReader,...
*/
public static void characterStream() {
try (Reader reader = new FileReader("D:\\Learning\\Java\\LearningJava\\file.txt")) {
char first = (char) reader.read(); // i
char second = (char) reader.read(); // n
char[] others = new char[12];
int number = reader.read(others); // 10
System.out.println(first + " " + second);
System.out.println(Arrays.toString(others));
System.out.println(number);
} catch (IOException e) {
System.out.println(e.getMessage());
}
// Mot cach khac de doc text data la doc tung ky tu cho den khi stream dong
try (FileReader reader = new FileReader("D:\\Learning\\Java\\LearningJava\\file.txt")) {
int charAsNumber = reader.read();
while(charAsNumber != -1) {
char character = (char) charAsNumber;
System.out.print(character);
charAsNumber = reader.read();
}
System.out.println();
} catch (IOException e) {
System.out.println(e.getMessage());
}
}
public static void byteStream() {
try (FileInputStream inputStream = new FileInputStream("D:\\Learning\\Java\\LearningJava\\file.txt")) {
byte[] bytes = new byte[5];
int numberOfBytes = inputStream.read(bytes);
System.out.println(numberOfBytes); // 5
System.out.println(Arrays.toString(bytes));
} catch (IOException e) {
System.out.println(e.getMessage());
}
}
}
##################################
5. threads
5.1. Main.java
public class Main {
public static void main(String[] args) {
//Main thread -> luong chinh
System.out.println("Start");
//Cach 1
//luong t
Thread t = new Thread(new Runnable() {
@Override
public void run() {
for (int i = 0; i < 100; i++) {
System.out.println("Thread 1 > " + i);
}
}
});
t.start();
//luong t2
Thread t2 = new Thread(new Runnable() {
@Override
public void run() {
for (int i = 0; i < 100; i++) {
System.out.println("Thread 2 > " + i);
}
}
});
t2.start();
//Cach2
new Thread(new Runnable() {
@Override
public void run() {
}
}).start();
//Lambda
new Thread(() -> {
}).start();
//.........
System.out.println("End");
}
}
######################################
5.2. Test.java
public class Test {
public static void main(String[] args) throws InterruptedException {
System.out.println("Thread main start");
ThreadOne threadOne = new ThreadOne();
threadOne.start();
ThreadTwo threadTwo = new ThreadTwo();
//new Thread(threadTwo).start();
Thread t2 = new Thread(threadTwo);
t2.start();
System.out.println("Noi luong 1 vao thread main.");
threadOne.join();
System.out.println("Noi luong 2 vao thread main.");
t2.join();
System.out.println("Thread main stop");
//sau 5s thi khong cho luong chay tiep
// try {
// Thread.sleep(5000);
// threadOne.stop();
// t2.stop();
// } catch (InterruptedException e) {
// // TODO Auto-generated catch block
// e.printStackTrace();
// }
}
}
#################################
5.3. Test2.java
public class Test2 {
public static void main(String[] args) throws InterruptedException {
System.out.println("Thread main start");
ThreadOne t1 = new ThreadOne();
Thread t2 = new Thread(new ThreadTwo(t1));
t1.start();
t2.start();
t2.join();
System.out.println("Thread main stop");
}
}
###################################
5.4. ThreadOne.java
public class ThreadOne extends Thread {
@Override
public void run() {
System.out.println("t1 is running");
for (int i = 0; i < 10; i++) {
System.out.println("Thread One >> " + i);
try {
Thread.sleep(500);
} catch (InterruptedException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}
}
}
#######################################
5.5. ThreadTwo.java
public class ThreadTwo implements Runnable{
ThreadOne t1;
//ham tao
public ThreadTwo() {
super();
}
public ThreadTwo(ThreadOne t1) {
super();
this.t1 = t1;
}
@Override
public void run() {
System.out.println("t2 is running");
try {
System.out.println("join t1 into t2");
t1.join();
System.out.println("t1 finish");
for (int i = 0; i < 10; i++) {
System.out.println("Thread Two >> " + i);
try {
Thread.sleep(1000);
} catch (InterruptedException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}
} catch (InterruptedException e1) {
// TODO Auto-generated catch block
e1.printStackTrace();
}
}
}
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