JAVA source.txt

Java Source Code





Hour 1




Example 1.1
public class Hi
{
   public static void main (String [ ] args)
   {
      System.out.print("Hello World");
   }
}




Example 1.2

package newPackage;

public class HelloWorld {

public static void main (String[] args){

System.out.print("Hello World!");
	
} 
}




Example 1.3
System.out.println ("Hello World");   // show "Hello World"
/*
 System.out.println( ) is a Java output command, meaning display or print.

*/




Example 1.4
System.out.print( "1 " ); 
System.out.print( "2 " );
System.out.print( "3"  );




Example 1.5
public class Hi{
public static void main ( String [ ] args ){    
System.out.print("  \" Hello World  \"  "); 
}
}




Example 1.6
const        continue



Example 1.7
"Very Good"
'S'
168
8f
true




Example 1.8
public static void main ( String [ ] args ) {
String mystring = "Hello World";
char  mychar = 'm';
int myinteger = 168168;
double myflt = 28.98;
boolean mybool = true;
}





Example 1.9
public class TryClass{
public static void main (String [ ] args){
int sum = 100 + 200;
String str = "We love" + "Java";
int incre = 10;  incre = ++incre;
System.out.println ( sum );   // Output:  300
System.out.println ( str );   //  Output:  We love Java.
System.out.println ( incre );  // Output:  11
}
}




Example 1.10
public class TryClass{
public static void main (String [ ] args){
boolean x=true;  boolean y=false;
boolean a, b, c;
a= x && y;   System.out.print (a);   // output: false
b=x || y;   System.out.print (b);   // output: true
c=! x;   System.out.print (c);   // output:  false
}
}





Example 1.11
int x=200; int y=100;
x+=y; System.out.print(x);
x-=y; System.out.print(x);
x/=y; System.out.print(x);
x%=y; System.out.print(x);




Example 1.12
int x=200; int y=100; 
boolean result1=(x>y); System.out.print(result1);
boolean result2=(x<=y); System.out.print(result2);
boolean result3=(x!=y ); System.out.print(result3);




Example 1.13
int a=100; int b=200;
String result1 = (a<b) ? "apple" : "banana";
System.out.print ( result1);
(Output:  apple)





Example 1.14
int a=100; int b=200;
String result2 = (a>b) ? "apple" : "banana";
System.out.print ( result2 );
(Output:  banana)




Hour 2





Example 2.1
public class TryClass{
public static void main (String [ ] args){
int a=200; 
int b=100;
if (a>b) {
System.out.print ( "a is greater than b.");
}}}




 

Example 2.2
public class TryClass{
public static void main (String [ ] args){
int a=100; int b=200;
if (a>b){
System.out.print ( "a is greater than b.");
}
else {
System.out.print ( "a is less than b");
}}} 





Example 2.3
public class TryClass{
public static void main (String [ ] args){
int number=20;
switch ( number ) {
case 10 : System.out.print ("Running case 10");  break;
case 20 : System.out.print ("Running case 20");  break;
case 30 : System.out.print ("Running case 30");  break;
default :  System.out.print ("Running default code");  break;  
}}} 





Example 2.4
public class TryClass{
public static void main (String [ ] args){
int x;
for (x = 0; x <= 5; x++) {
System.out.print( x );
}}}




Example 2.5
public class TryClass{
public static void main (String [ ] args){
int counter=0;
while (counter < 8){
System.out.print  ("&");
counter++;
}}} 




Example 2.6
public class TryClass{
public static void main (String [ ] args){
int counter=0;
do {
System.out.print ( "@");
counter++;
} while (counter<8);
}} 




Example 2.7
public class TryClass{
public static void main (String [ ] args){
int num=0;
while (num<10){
if (num==5)  break;
num++;
}
System.out.print( num );
}} 





Example 2.8
public class TryClass{
public static void main (String [ ] args){
int num=0;
while (num<10){
num++;
if (num==5)  continue;
System.out.print( num );
}}}




Example 2.9
public class TryClass{
public static void main (String [ ] args){
int num=10;
if( num ){    // error
System.out.print ("No good");
}
while ( num ){     // error
System.out.print ("No good");
}}} 





Hour 3





Example 3.1
int myarray[ ] = { 10,20,30,40 };




Example 3.2
int myArray[ ] = new int [3];
myArray [0] = 100;
myArray [1] = 200;
myArray [2] = 300;




Example 3.3
public class TryClass{
public static void main (String [ ] args){
int arr[ ] = {10,20,30};
int num = arr.length;
System.out.print ( num );
}} 




Example 3.4
int arr[ ] = {10, 20, 30, 40, 50};
int value = arr[2];
System.out.println ( value );
( Output: 30)





Example 3.5
 int num[ ] = new int [5];
num[2] = 800;
System.out.println ( num[2]);
( Output:  800)




Example 3.6
package tryPackage;
import java.util.Arrays;
public class TryClass{
public static void main (String [ ] args){
String myarray[ ] = { "Cat", "Apple", "Dog", "Boy"};
Arrays.sort (myarray);
for(int num=0; num<myarray.length; num++){
System.out.print (myarray[num]+" ");
}}}




Example 3.7
float num = 10.2f;
System.out.print( Math.round(num) );




Example 3.8
public class TryClass{
public static void main (String [ ] args){
float num = 9.5f;
System.out.println( "Ceiling number is "+Math.ceil( num ) );
System.out.println( "Flooring number is "+Math.floor( num ) );
}} 




Example 3.9
public class TryClass{
public static void main (String [ ] args){
int x = 100;
int y = 200;
System.out.println("Greater number is "+Math.max(x, y) );
System.out.println("Less number is "+Math.min(x, y) );
}}




Example 3.10
public class TryClass{
public static void main (String [ ] args){
int num = 4;
System.out.println("Square number is "+Math.pow(num,2) );
System.out.println("Square root is "+Math.sqrt(num) );
}}




Example 3.11
public class TryClass{
public static void main (String [ ] args){
double pi = Math.PI;
double ran = Math.random( );
System.out.println("The PI value is" + pi);
System.out.println("The random number is" + ran);
}} 






Hour 4





Example 4.1
public class TryClass{
public static void main (String [ ] args){
String str = "This is a string";
int length = str.length( );
System.out.println( "The size of string is " + length);
}} 




Example 4.2
String str1 = "Very";  String str2 = "Good";
System.out.print( str1 + str2);
( Output: Very Good )

String str1 = "Very";  String str2 = "Good";
System.out.print( str1.concat (str2));
( Output: Very Good )





Example 4.3
public class TryClass{
public static void main (String [ ] args){
String str1="Good", str2="Good";
System.out.print(str1.equals (str2));
System.out.print("Good".equals ("Good"));
}} 




Example 4.4
public class TryClass{
public static void main(String args[]) {
String str = "Very Good";
char result = str.charAt(5);
System.out.println( result );
}}




Example 4.5
public class TryClass{
public static void main(String args[ ]) { 
String str = "Very Good";
System.out.println(str.indexOf( "y" ));
}}




Example 4.6
public class TryClass{
public static void main(String args[ ]) { 
String Str = "Very Good";
System.out.println(Str.substring(5, 7) );
}}




Example 4.7
public class TryClass{
public static void main(String args[ ]){
String Str = "Very Good"; System.out.println(Str.toUpperCase( ) );
System.out.println(Str.toLowerCase( ) );
}}




Example 4.8
public class TryClass{
public static void main(String args[ ]){
String Str = "Very Good";
System.out.println( Str.replace("Good", "Well") );
}} 




Example 4.9
public class TryClass{
public static void main(String args[ ]){
int num = 169;  
String str = "       Good        ";   // Note that spaces.
String str1 = Integer.toString( num );
String str2 = str.trim( );
System.out.println( str1+" is a String" );
System.out.println( str2+"is trimmed" ); 
}} 




Example 4.10
StringBuffer sb = new StringBuffer ( "abcde" );
sb.insert ( 2, "123");    // Output:  abc123de
sb.append ( "456");    // Output:  abc123de456
sb.reverse ( );    // Output:  654ed321cba





Hour 5





Example 5.1
public class TryClass{
public static void main(String args[ ]){
myMethod( );  }
public static void myMethod ( ) {
System.out.print( "This is a method" );
}} 




Example 5.2
public class TryClass{
public static void main ( String [ ] args ) { 
myMethod( "ABC" );
}
public static void myMethod ( String argument ) {
System.out.print( "This is a method " + argument );
}} 




Example 5.3
public class TryClass{
public  static void main ( String [ ] args ) { 
int num=10;
System.out.print ("The number is  "+myMethod( num ));
}
static int myMethod ( int arg ) {
return ++arg;
}}




Example 5.4
public class Color {
String c1, c2;
void brightness ( ) {  System.out.print ("blue"); }
}




Example 5.5
obj = new Color(  );
obj.c1= "yellow";   obj.c2="purple";
obj.brightness ( );   // brightness( ){ } in previous page.




Example 5.6
public class Color {
String c1, c2;
Color ( ) {  c1="yellow";  c2="purple"; }  // constructor
}





Example 5.7
package correctPackage;

class Color{  String x,y;   // declare two variables
Color ( String a, String b) { x=a; y=b; } 
Color ( ) {  x="yellow ";  y="purple ";}  

public static void main (String args[ ]) {
Color obj1=new Color("green ", "orange ");  
Color obj2=new Color(  );   
System.out.println(obj1.x +  obj1.y);
System.out.println(obj2.x +  obj2.y);
}
}





Example 5.8
package correctPackage;
class MyClass {
int num;
void test(int num) {  
 this.num=num; 
 System.out.println( this.num );
};
public static void main(String[ ] args) {
 MyClass obj = new MyClass( );
 obj.test(10);
}
}




Example 5.9
class MyClass { 
int x, y;
MyClass ( ) {
this ( 100, 200 );
 }
MyClass ( int a, int b)
x=a;  y=b;
}




Example 5.10
class point {
int x= 100, y = 200;   //  instance variable
void test( ){ 
int x = 1, y = 2;     //  local variable
}
}






Hour 6





Example 6.1
class parent_class{
// define variable;
// define method;
}
class sub_class extends parent_class{ 
// define variable;
// define method;
}




Example 6.2
class super_class{
super_class (int x, int y){   // constructor 
this.x=x;  this .y=y;
}
}
class sub_class extends super_class{ 
sub_class(int x, int y){   // constructor
super ( x,y );
}
}




Example 6.3
class Super_class{
int test( int num ) { return num; }
}
class Sub_class extends Super_class{ 
int test( int num ) { return 100 + num; }
}
public class OverridingClass {
public static void main (String args[ ]){
Sub_class obj=new Sub_class( );
System.out.print( obj.test( 200 ));
}}




Example 6.4 (overloading)
class Color{  String x,y;   // declare two variables
Color ( String a, String b) { x=a; y=b; } 
Color ( ) {  x="yellow";  y="purple";}  
}





Example 6.5 (overriding)
class super_class{
int test( int num ) { return num; }
}
class sub_class extends super_class{ 
int test( int num ) { return 100 + num; }
}




Example 6.6
class MyClass {
static int count=100;
public static void main (String args[ ]){
System.out.print(  MyClass.count );
}
}





Example 6.7
class MyClass {
static int count( ){ return 100 ;}
public static void main (String args[ ]){
System.out.print(  MyClass.count( ) );
}}




Example 6.8
class MyClass{
final int x =100;
static void test(  ){ x = 200;}   // error
public static void main (String args[ ]){
System.out.print(  MyClass.test( ) );
}
}




Example 6.9
class animal{
final void test ( ){ 
System.out.print("animal");
}
}
class dog extends animal {
void test ( ){    // error
System.out.print("dog");
}
}




Example 6.10
final class animal {
//  define some variables;
//  define some method;
}
class elephant extends animal {   // error
//  define some variables;
//  define some method;
}



Example 6.11
class Animal{
void cry( ){
System.out.println("crying......");;
}
}
class Dog extends Animal{
void cry( ){
System.out.println("Wow, Wow......");
}
}
class Cat extends Animal{
void cry( ){
System.out.println("Meow, Meow......");
}
}
class PolymorphismDemo{
public static void main(String args[ ]){
Animal animalVar;
animalVar = new Dog( );
animalVar.cry( );
animalVar = new Cat( );
animalVar.cry( );
}
}




Example 6.12  (in file1)
package myPackage;    
class MyClass1 {¡­}
class MyClass2 {¡­}






Example 6.13 (in file2)
package myPackage;    
import myPackage.*;  





Example 6.14
(In Drive.java)
package myPackage;
public class Drive{
public void getDistance (int mph, float time){
System.out.println("SPEED:" + mph + " MILES/HOUR");
System.out.println("TIME:" + time + " HOURS");
System.out.println("DISTANCE:" + time*mph + " MILES");
}
}


(In TestDrive.java)
package myPackage;
import myPackage.Drive;
public class TestDrive{
  public static void main (String args[ ]) {
	Drive myDrive = new Drive( );
	myDrive.getDistance(120, 5);
}
}





Hour 7




Example 7.1
abstract class books{   //define a abstract class
abstract int read( );   //define a abstract method
}
class eBooks extends books{   //extend the parent class
int read ( ){ return 100; }  //implement abstract method
}




Example 7.2
There two files in the same package as following:

(In file1 of myPackage) 
package myPackage;
public class ParentClass{   
int num=100;   // This is a default member.
}

 (In file2 of myPackage)
package myPackage;
public class SubClass extends ParentClass{
public static void main(String[] args) {
SubClass s=new SubClass( );
System.out.print ( s.num );  
}
}  




Example 7.3
There two files in the different package as following:

(In file1 of MyPackage)
package myPackage;
public class ParentClass{   
public int num=100;   // This is a public member.
}
 
(In file2 of NewPackage)
package newPackage;
import myPackage.ParentClass;
public class SubClass extends ParentClass{
public static void main(String[] args) {
SubClass s=new SubClass( );
System.out.print ( s.num );  
}
}  




Example 7.4
class MyClass { 
private MyClass( ){  // private constructor
System.out.print("OK!");
}}
public class NewClass{ 
public static void main ( String args [ ] ) {
MyClass mc=new MyClass ( );   // error
}}




Example 7.5
There two files in the different package as following:

(In file1 of MyPackage)
package myPackage;
public class ParentClass{   
protected int num=100;   // protected member.
}

(In file2 of NewPackage)
package newPackage;
import myPackage.ParentClass;
public class SubClass extends ParentClass{
public static void main(String[] args) {
SubClass s=new SubClass( );
System.out.print ( s.num );  
}
} 




Example 7.6
interface books {   // define an interface
int booknumber( );    //  define an empty method
}
class eBooks implement books {  //  implement interface
public int booknumber ( ) {  // implement method
 return 100;  
}  }




Example 7.7
class Book {  //  create a class
public String title;  
public int number;
public Book ( ) {   //  define a constructor
title = "Learning Java ";  // initialization
number = 100;  // initialization
}}
public class Publisher {   // create main class
public static void main ( String args [ ]) { //main method
Book eBook = new Book ( );   // create an object
System.out.print( eBook.title + eBook.number); 
}}




Example 7.8
class AnotherClass{    // define another class
public static void AnotherMethod( ){ // another method
System.out.print ( "Very Good" ); }
}
public class MainClass{   //define main class
public static void main (String args [ ]){ // main method
AnotherClass.AnotherMethod( ); //call another method
}
}





Hour 8





Example 8.1
public class ExceptionSample {
public static void main (String args [ ]) {
int a=10, b=0, c;
c = a/b;   // error
System.out.print ( c );
}
}




Example 8.2
public class ExceptionSample {
public static void main (String args [ ]) {
try {
int a=10, b=0, c;
c = a/b;   // error
System.out.print ( c );
}
catch ( ArithmeticException e) {
System.out.print (" Divided By Zero ");
}}} 




Example 8.3
public class ExceptionSample {
public static void main (String args [ ]) {
try {
int a[ ] = new int [10];
a[10]=100;  // error
System.out.print ( a[10] );
}
catch ( ArrayIndexOutOfBoundsException e) {
System.out.print (" Array index out of bounds ");
}}} 




Example 8.4
public class ExceptionSample {
public static void main (String args [ ]) {
try {
char ch = "ABC".charAt(100);  // error
System.out.print ( ch );
}
catch (IndexOutOfBoundsException e) {
System.out.print ( "Character index out of bounds" );
}}} 





Example 8.5
public class ExceptionSample {
public static void main (String args [ ]) {
try {
char ch = "ABC".charAt(100);  // error
}
catch (IndexOutOfBoundsException e) {
System.out.print ( "Character index out of bounds. " );
}     //  Output: Character index out of bounds
finally {  System.out.print("The End"); }
}} 
 




Example 8.6
public class ExceptionSample {
public static void main (String args [ ]) {
try {
int a[ ] = new int[10];
if ( a[10] >0 ) throw new ArrayIndexOutOfBoundsException("Error");
}    // the last element is a[9], without a[10].
catch ( ArrayIndexOutOfBoundsException e) {
System.out.print ("Error index:"+e.getMessage( ));
}}} 




Example 8.7
public class ExceptionSample {
public static void main (String args [ ]) {
try {
int b = 0;
calculate( b );
}
catch( Exception e) {
System.out.println("The error is"+ e.getMessage( ));
}}
public static int calculate( int num) throws ArithmeticException {
int a=10, c;
c = a/num;   // num is 0, error
return c;
}
}  




Example 8.8
File f = new File ( MyFile );
if (f.exists( )) {
System.out.println("Exists:"+ f.exists());    //Exists: true
System.out.println("Can read:"+ f.canRead());  //Can read: true
System.out.println("Can write:"+ f.canWrite());  //Can write: false
System.out.println("Is file:"+ f.isFile());  // Is file: true
}




Example 8.9  
 (Prepare an empty file "MyFile.txt" in the same project folder with the following Java file OutputFile.java)

package myPackage;
import java.io.*;
public class OutputFile {
public static void main(String[] args) {
char ch;
int number;
try{
FileOutputStream fout = new FileOutputStream("MyFile.txt");
System.out.println("Please input some words, finish with # key and enter:");
while((ch = (char)System.in.read())!= '#')  //read inputed characters from keyboard
fout.write(ch);  // write characters to file
fout.close();
}
catch(FileNotFoundException e){			
System.err.println(e);	
}
catch(IOException e){
System.err.println(e);
}
}
}





Example 8.10    
 (Given MyFile.txt content is "C++ is very good!" in the same project folder with following Java file InputFile.java)

package myPackage;
import java.io.*;
public class InputFile {
public static void main(String[] args) {
char ch;
int number;
try{
FileInputStream fin = new FileInputStream("MyFile.txt");
while((number=fin.read())!= -1)  // read file
System.out.print((char)number);  // change to characters
fin.close();
}
catch(FileNotFoundException e){			
System.err.println(e);	
}
catch(IOException e){
System.err.println(e);
}}}




Example 8.11
public class ThreadDemo extends Thread{
public void run( ){
for(int i = 0; i<3; i++){
System.out.println("Thread!");
}}
public static void main(String[ ] args){
ThreadDemo myThread = new ThreadDemo( );
myThread.start( );
}}




Example 8.12
class ThreadDemo implements Runnable{
public void run( ){
for(int i = 0; i<3; i++){
System.out.println("Thread!");}
}
public static void main(String[ ] args){
Thread myThread = new Thread(new ThreadDemo( ));
myThread.start( );  
}}




Example 8.13
class ThreadDemo extends Thread{
public ThreadDemo(String threadName){
super(threadName);  // initialize thread name
}
public void run( ){
for(int i = 0; i<2; i++){
System.out.println(getName( ) + " running!");
}}}
public class UseThread{
public static void main(String[ ] args){
ThreadDemo myThread1 = new ThreadDemo("1st thread");
ThreadDemo myThread2 = new ThreadDemo("2nd thread");
ThreadDemo myThread3 = new ThreadDemo("3rd thread");
myThread1.start();
myThread2.start();
myThread3.start();
}}




Example 8.14
class ThreadDemo implements Runnable{
public void run( ){
¡­¡­
wait( );
¡­¡­
}
}
Class TextThread{
public static void main(String args[ ]){
Thread myThread = new Thread(newThreadDemo( ));
myThread.start( );
Thread.sleep(1000);
notify( );
Thread.yield( );
}
}