how to read to into a file in java

try(BufferedReader br = new BufferedReader(new FileReader("file.txt"))) {
    StringBuilder sb = new StringBuilder();
    String line = br.readLine();

    while (line != null) {
        sb.append(line);
        sb.append(System.lineSeparator());
        line = br.readLine();
    }
    String everything = sb.toString();
}

// Java Program to illustrate reading from 
// FileReader using FileReader 
import java.io.*; 
public class ReadingFromFile 
{ 
  public static void main(String[] args) throws Exception 
  { 
    // pass the path to the file as a parameter 
    FileReader fr = 
      new FileReader("C:\\Users\\pankaj\\Desktop\\test.txt"); 
  
    int i; 
    while ((i=fr.read()) != -1) 
      System.out.print((char) i); 
  } 
} 

// Java Program to illustrate reading from FileReader 
// using BufferedReader 
import java.io.*; 
public class ReadFromFile2 
{ 
  public static void main(String[] args)throws Exception 
  { 
  // We need to provide file path as the parameter: 
  // double backquote is to avoid compiler interpret words 
  // like \test as \t (ie. as a escape sequence) 
  File file = new File("C:\\Users\\pankaj\\Desktop\\test.txt"); 
  
  BufferedReader br = new BufferedReader(new FileReader(file)); 
  
  String st; 
  while ((st = br.readLine()) != null) 
    System.out.println(st); 
  } 
} 

// Creating a text File using FileWriter 
import java.io.FileWriter; 
import java.io.IOException; 
class CreateFile 
{ 
    public static void main(String[] args) throws IOException 
    { 
        // Accept a string  
        String str = "File Handling in Java using "+ 
                " FileWriter and FileReader"; 
  
        // attach a file to FileWriter  
        FileWriter fw=new FileWriter("output.txt"); 
  
        // read character wise from string and write  
        // into FileWriter  
        for (int i = 0; i < str.length(); i++) 
            fw.write(str.charAt(i)); 
  
        System.out.println("Writing successful"); 
        //close the file  
        fw.close(); 
    } 
}

// Java Program to illustrate reading from FileReader 
// using Scanner Class reading entire File 
// without using loop 
import java.io.File; 
import java.io.FileNotFoundException; 
import java.util.Scanner; 
  
public class ReadingEntireFileWithoutLoop 
{ 
  public static void main(String[] args) 
                        throws FileNotFoundException 
  { 
    File file = new File("C:\\Users\\pankaj\\Desktop\\test.txt"); 
    Scanner sc = new Scanner(file); 
  
    // we just need to use \\Z as delimiter 
    sc.useDelimiter("\\Z"); 
  
    System.out.println(sc.next()); 
  } 
}