1. Inheritance
class A {
int x;
int y;
int get(int p, int q){
x=p; y=q; return(0);
}
void Show(){
System.out.println(x);
}
}
class B extends A{
public static void main(String args[]){
A a = new A();
a.get(5,6);
a.Show();
}
void display(){
System.out.println("B");
}
}
string
import java.util.Scanner;
class Compare_Strings
{
public static void main(String args[])
{
String s1, s2;
Scanner in = new Scanner(System.in);
System.out.println("Enter the first string");
s1 = in.nextLine();
System.out.println("Enter the second string");
s2 = in.nextLine();
if ( s1.compareTo(s2) > 0 )
System.out.println("First string is greater than second.");
else if ( s1.compareTo(s2) < 0 )
System.out.println("First string is smaller than second.");
else
System.out.println("Both strings are equal.");
}
}
Stringbuffer
public class StringBufferDemo {
public static void main(String[] args) {
// Examples of Creation of Strings
StringBuffer strBuf1 = new StringBuffer("Bob");
StringBuffer strBuf2 = new StringBuffer(100); //With capacity 100
StringBuffer strBuf3 = new StringBuffer(); //Default Capacity 16
System.out.println("strBuf1 : " + strBuf1);
System.out.println("strBuf2 capacity : " + strBuf2.capacity());
System.out.println("strBuf3 capacity : " + strBuf3.capacity());
}
}
Try catch
class Exc2 {
public static void main(String args[]) {
int d, a;
try { // monitor a block of code.
d = 0;

2. a = 42 / d;
System.out.println("This will not be printed.");
} catch (ArithmeticException e) { // catch divide-by-zero
error
System.out.println("Division by zero.");
}
System.out.println("After catch statement.");
}
}
thread
// Create a new thread.
class NewThread implements Runnable {
Thread t;
NewThread() {
// Create a new, second thread
t = new Thread(this, "Demo Thread");
System.out.println("Child thread: " + t);
t.start(); // Start the thread
}
// This is the entry point for the second thread.
public void run() {
try {
for(int i = 5; i > 0; i--) {
System.out.println("Child Thread: " + i);
// Let the thread sleep for a while.
Thread.sleep(500);
}
} catch (InterruptedException e) {
System.out.println("Child interrupted.");
}
System.out.println("Exiting child thread.");
}
}
class ThreadDemo {
public static void main(String args[]) {
new NewThread(); // create a new thread
try {
for(int i = 5; i > 0; i--) {
System.out.println("Main Thread: " + i);
Thread.sleep(1000);
}
} catch (InterruptedException e) {
System.out.println("Main thread interrupted.");
}
System.out.println("Main thread exiting.");
}
}
Reading and writing file
class FileStreamsReadnWrite {
public static void main(String[] args) {
try {
File stockInputFile = new File("C://stock/stockIn.txt");
File StockOutputFile = new File("C://stock/StockOut.txt");
/*
* Constructor of FileInputStream throws FileNotFoundException if
* the argument File does not exist.
*/
FileInputStream fis = new FileInputStream(stockInputFile);
FileOutputStream fos = new FileOutputStream(StockOutputFile);
int count;
while ((count = fis.read()) != -1) {
fos.write(count);
}
fis.close();
fos.close();
} catch (FileNotFoundException e) {
System.err.println("FileStreamsReadnWrite: " + e);
} catch (IOException e) {
System.err.println("FileStreamsReadnWrite: " + e);
}

3. }
}