File Handling programs

Author: akash-coded

StringCombining.java

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+public class StringCombining {
+    public static void main(String[] args) {
+        String str1 = new String("Wiley");
+        StringBuffer str2 = new StringBuffer("Google");
+
+        System.out.println(str1.hashCode());
+        str1 = str1.concat(" Pvt. Ltd.");
+        System.out.println(str1.hashCode());
+
+        str2.append(" Ltd.");
+
+        System.out.println(str1);
+        System.out.println(str2);
+    }
+}

StringInternNitish.java

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+public class StringInternNitish {
+    public static void main(String args[]) {
+
+        String str0 = new String("hlo");
+        String str1 = "hlo";
+        String str2 = "hlo";
+        String str4 = str0.intern();
+        System.out.println(str0 == str4); // false
+        System.out.println(Integer.toHexString(str4.hashCode()));
+        System.out.println(Integer.toHexString(str0.hashCode()));
+    }
+}

StringTokenizerExample.java

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+import java.util.StringTokenizer;
+
+public class StringTokenizerExample {
+    public static void main(String[] args) {
+        StringTokenizer tokenizer = new StringTokenizer("Akash,Kumar Das", " ");
+        while (tokenizer.hasMoreTokens()) {
+            System.out.println(tokenizer.nextToken());
+        }
+    }
+}

fileHandling/CreateFile.java

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+package fileHandling;
+
+import java.io.File;
+import java.io.IOException;
+
+public class CreateFile {
+    public static void main(String[] args) throws IOException {
+        File f = new File("fileHandling/Test2.txt");
+        if (f.createNewFile()) {
+            System.out.println("File created successfully");
+        } else {
+            System.out.println("File already exists");
+        }
+    }
+}

fileHandling/DeleteFile.java

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+package fileHandling;
+
+import java.nio.file.DirectoryNotEmptyException;
+import java.nio.file.Files;
+import java.nio.file.NoSuchFileException;
+import java.nio.file.Paths;
+import java.io.File;
+import java.io.FileNotFoundException;
+import java.io.IOException;
+
+public class DeleteFile {
+    public static void main(String[] args) {
+        File f = new File("Test.txt");
+        if (f.delete()) {
+            System.out.println(f.getName() + " deleted.");
+        } else {
+            System.out.println("Unexpected error encountered while trying to delete " + f.getName());
+        }
+
+        try {
+            Files.deleteIfExists(Paths.get("Empty"));
+            System.out.println("Deleted successfully");
+        } catch (FileNotFoundException e) {
+            System.out.println("File was not found");
+        } catch (NoSuchFileException e) {
+            System.out.println("Sorry, file not found!");
+        } catch (DirectoryNotEmptyException e) {
+            System.out.println("Directory not empty");
+        } catch (IOException e) {
+            e.printStackTrace();
+        }
+    }
+}

fileHandling/GetFileInfo.java

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+package fileHandling;
+
+import java.io.File;
+import java.io.IOException;
+
+public class GetFileInfo {
+    public static void main(String[] args) {
+        File f = new File("fileHandling/Test.txt");
+
+        if (f.exists()) {
+            System.out.println(f.getName());
+
+            System.out.println(f.getAbsolutePath());
+
+            System.out.println(f.canRead());
+
+            System.out.println(f.canWrite());
+
+            System.out.println(f.canExecute());
+
+            System.out.println(f.length());
+        }
+    }
+}

fileHandling/ReadFromFile.java

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+package fileHandling;
+
+import java.util.Scanner;
+import java.nio.file.Files;
+import java.nio.file.Paths;
+import java.io.BufferedReader;
+import java.io.File;
+import java.io.FileReader;
+import java.io.FileNotFoundException;
+import java.io.IOException;
+
+public class ReadFromFile {
+    public static void main(String[] args) {
+        // the general way
+        File f = new File("fileHandling/Test.txt");
+
+        try (Scanner fileReader = new Scanner(f);) { // try-with-resources
+            while (fileReader.hasNextLine()) {
+                System.out.println(fileReader.nextLine());
+            }
+        } catch (FileNotFoundException e) {
+            e.printStackTrace();
+        }
+
+        // nio way of reading from file
+        try (BufferedReader reader = Files.newBufferedReader(Paths.get("fileHandling/Test2.txt"))) {
+            String currentLine = null;
+            while ((currentLine = reader.readLine()) != null) {// while there is content on the current line
+                System.out.println(currentLine); // print the current line
+            }
+        } catch (IOException ex) {
+            ex.printStackTrace(); // handle an exception here
+        }
+
+        // using FileReader (reads character by character)
+        try (FileReader fileReader = new FileReader("fileHandling/Test.txt");) {
+            int ch;
+            int counter = 0;
+            while ((ch = fileReader.read()) != -1) {
+                System.out.print((char) ch);
+                counter++;
+            }
+            System.out.println(counter);
+        } catch (IOException ex) {
+            ex.printStackTrace(); // handle an exception here
+        }
+    }
+}

fileHandling/Test.txt

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+This is a test file for file handling.
+Second line.

fileHandling/Test2.txt

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+File Handling test file. Dummy text. Appended via FileWriter. Appended via nio Files.

fileHandling/Test3.txt

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+Appended via FileWriter

fileHandling/Test4.txt

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+Appended via nio.Files

fileHandling/WriteFile.java

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+package fileHandling;
+
+import java.io.FileWriter;
+import java.io.IOException;
+import java.nio.file.Files;
+import java.nio.file.Paths;
+import java.nio.file.StandardOpenOption;
+
+public class WriteFile {
+    public static void main(String[] args) throws IOException {
+        // Create or Overwrite a file
+        FileWriter writer = new FileWriter("fileHandling/Test2.txt");
+        writer.write("This is my 2nd file handling test file.");
+        writer.write("Dummy text.");
+        writer.close();
+        System.out.println("File written successfully");
+
+        // Append to a file
+        FileWriter writer2 = new FileWriter("fileHandling/Test2.txt", true);
+        writer2.write("Appended via FileWriter");
+        writer2.close();
+        System.out.println("File written successfully");
+
+        // Java 7 onwards
+        Files.write(Paths.get("fileHandling/Test2.txt"), "Appended via nio.Files".getBytes(), StandardOpenOption.CREATE,
+                StandardOpenOption.APPEND);
+    }
+}

fileHandling/delete

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+package quiz;
+
+public class Quiz1 {
+    public static void main(String[] args) {
+        System.out.println(Integer.parseInt("ab10"));
+    }
+}
+
+// 1. public class LineUp {
+// 2. public static void main(String[] args) {
+// 3. double d = 12.345;
+// 4. // insert code here
+// 5. }
+// 6. }
+
+// Expected Output: | 12.345|
+
+// Options
+// A. System.out.printf("|%7d| \n", d);
+// B. System.out.printf("|%7f| \n", d);
+// C. System.out.printf("|%3.7d| \n", d);
+// D.System.out.printf("|%3.7f| \n",d);
+// E. System.out.printf("|%7.3d| \n", d);
+// F. System.out.printf("|%7.3f| \n", d);
+
+// public class Test {
+// public static void main(String [] args) {
+// int x = 5;
+// boolean b1 = true;
+// boolean b2 = false;
+
+// if ((x == 4) && !b2 )
+// System.out.print("1 ");
+
+// System.out.print("2 ");
+
+// if ((b2 = true) && b1 )
+// System.out.print("3 ");
+// }
+// }
+
+// A. 2
+// B. 3
+// C. 1 2
+// D. 2 3
+// E. 1 2 3
+// F. Compilation fails.
+// G. An exception is thrown at runtime.
+
+// interface Foo {}
+// class Alpha implements Foo {}
+// class Beta extends Alpha {}
+
+// class Delta extends Beta {
+// public static void main(String[] args) {
+// Beta x = new Beta();
+// //insert code here 16
+// }
+// }
+
+// Which code, inserted at line 16, will cause a java.lang.ClassCastException?
+
+// A.Alpha a = x;
+// B.Foo f = (Delta) x;
+// C.Foo f = (Alpha) x;
+// D.Beta b = (Beta)(Alpha)x;
+
+// public void go() {
+// String o = "";
+// z: for (int x = 0; x < 3; x++) {
+// for (int y = 0; y < 2; y++) {
+// if (x == 1)
+// break;
+// if (x == 2 && y == 1)
+// break z;
+// o = o + x + y;
+// }
+// }
+// System.out.println(o);
+// }
+
+// What is
+// the result
+// when the
+
+// go() method is invoked?
+
+// A. 00
+// B. 0001
+// C. 000120
+// D. 00012021
+// E. Compilation fails.
+// F. An exception is thrown at runtime.
+
+// try {
+// //some code here line 108
+// } catch (NullPointerException e1) {
+// System.out.print("a");
+// } catch (Exception e2) {
+// System.out.print("b");
+// }finally {
+// System.out.print("c");
+// }
+
+// If some sort of exception is thrown at line 108, which output is possible?
+
+// A. a
+// B. b
+// C. c
+// D. ac
+// E. abc