This blog is to demonstrate a simple way to use IO stream FileReader and FileWriter.
we can use FileReader to read text from an existing file（read in character）, and print text in the terminal; use FileWriter to write content to certain file. the file will be created if it doesn't exist in the current directory.
One thing to remember, if we use IDEA, we should create a file named "temp.txt" with some words in the root directory of the current project when we use FileReader to read from the file.
Demo of FileReader
import java.io.FileNotFoundException;
import java.io.FileReader;
import java.io.IOException;
public class FileReaderTest01 {
public static void main(String[] args) {
// Create FileReader object
FileReader fr = null;
try {
fr = new FileReader("temp.txt");
char[] chars = new char[4];
int readCount = 0;
// Keep reading until reaching the last word
while ((readCount = fr.read(chars)) != -1) {
System.out.print(new String(chars, 0, readCount));
}
} catch (FileNotFoundException e) {
e.printStackTrace();
} catch (IOException e) {
e.printStackTrace();
} finally {
if (fr != null) {
try {
// close the stream
fr.close();
} catch (IOException e) {
e.printStackTrace();
}
}
}
}
}
Demo of FileWriter
import java.io.FileWriter;
import java.io.IOException;
public class FileWriterTest01 {
public static void main(String[] args) {
// create FileWriter object fw
FileWriter fw = null;
try {
// the file will be created if it does not exist
fw = new FileWriter("file",true);
// can run multiple times, and observe the results
fw.write("Hello Java ");
// do not forget to flush
fw.flush();
} catch (IOException e) {
e.printStackTrace();
}finally {
if (fw != null) {
try {
// remember to close the stream
fw.close();
} catch (IOException e) {
e.printStackTrace();
}
}
}
}
}
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