3. Essential Java Classes 5. Some Useful Classes презентация

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1. 3. Essential Java Classes 5. Some Useful Classes
2. Class System (1 of 2) contains several
3. Class System (2 of 2) exit(int status) -
4. Class Runtime Allows to interface with the
5. Example of String Command Execution Runtime r
6. Class Properties represents a persistent set of
7. Configuration File Example dbpassword=pass&word database=localhost dbuser=vmo * Infopulse training Center
8. Use Properties Example Properties applicationProps = new
9. Class Object (1 of 2) The root
10. Class Object (2 of 2) equals(Object obj) -
11. Class Random is used to generate a
12. Class Math (1 of 2) Contains methods
13. Class Math (2 of 2) sqtr(double value)

Class System (1 of 2) contains several useful class fields and methods it cannot be instantiated standard input, standard output, and error output streams gets and sets system properties *

Слайд 13. Essential Java Classes
5. Some Useful Classes

Слайд 2Class System (1 of 2)
contains several useful class fields and methods
it

cannot be instantiated
standard input, standard output, and error output streams
gets and sets system properties

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Слайд 3Class System (2 of 2)
exit(int status) - terminates the currently running Java

Virtual Machine
gc() - runs the garbage collector
arraycopy(…) - copies an array
console() - Returns the unique Console object associated with the current JVM
nanoTime() - Returns the current value of the running JVM high-resolution time
See http://docs.oracle.com/javase/7/docs/api/java/lang/System.html for details

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Слайд 4Class Runtime
Allows to interface with the environment in which the application

is running
static getRuntime() - Returns the runtime object associated with the current Java application
freeMemory() - returns the amount of free memory in the JVM
totalMemory() - returns the total amount of memory in the JVM.

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Слайд 5Example of String Command Execution
Runtime r = Runtime.getRuntime();
try{

r.exec("C:\\Program Files\\Mozilla Firefox\\firefox.exe");
}
catch(Exception ex){
System.out.println(ex.getMessage());
}

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Слайд 6Class Properties
represents a persistent set of properties as pairs of key-value
details

are here:
http://docs.oracle.com/javase/tutorial/essential/environment/properties.html

http://docs.oracle.com/javase/7/docs/api/java/util/Properties.html

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Слайд 7Configuration File Example
dbpassword=pass&word
database=localhost
dbuser=vmo

*
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Слайд 8Use Properties Example
Properties applicationProps = new Properties();
in = new FileInputStream("appProperties");
applicationProps.load(in);
in.close();

String dbInfo = applicationProps. getProperty("database");

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Слайд 9Class Object (1 of 2)
The root of the class hierarchy
Every class

has Object as a superclass
All objects, including arrays, implement the methods of this class

See http://docs.oracle.com/javase/7/docs/api/java/lang/Object.html for details

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Слайд 10Class Object (2 of 2)
equals(Object obj) - indicates whether some other object

is "equal to" this one
getClass() - returns the runtime class of this Object
clone() - creates and returns a copy of this object
toString() - returns a string representation of the object

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Слайд 11Class Random
is used to generate a stream of pseudorandom numbers
Random(long seed) -

creates a new random number generator
nextInt() - returns the next pseudorandom, uniformly distributed int value
nextInt(int n) - returns a pseudorandom, uniformly distributed int value between 0 (inclusive) and the specified value (exclusive)
See http://docs.oracle.com/javase/7/docs/api/java/util/Random.html for details

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Слайд 12Class Math (1 of 2)
Contains methods for performing basic numeric operations:

elementary exponential,
logarithm,
square root
trigonometric functions
See http://docs.oracle.com/javase/7/docs/api/java/lang/Math.html for details

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Слайд 13Class Math (2 of 2)
sqtr(double value)
exp(double value)
log(double value)
power(double value, double p)
sin(double

value)
sinh(double value)
toRadians(double value)

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3. Essential Java Classes 5. Some Useful Classes презентация

Содержание

Слайд 13. Essential Java Classes
5. Some Useful Classes

Слайд 2Class System (1 of 2)
contains several useful class fields and methods
it

Слайд 3Class System (2 of 2)
exit(int status) - terminates the currently running Java

Слайд 4Class Runtime
Allows to interface with the environment in which the application

Слайд 5Example of String Command Execution
Runtime r = Runtime.getRuntime();
try{

Слайд 6Class Properties
represents a persistent set of properties as pairs of key-value
details

Слайд 7Configuration File Example
dbpassword=pass&word
database=localhost
dbuser=vmo

*
Infopulse training Center

Слайд 8Use Properties Example
Properties applicationProps = new Properties();
in = new FileInputStream("appProperties");
applicationProps.load(in);
in.close();

Слайд 9Class Object (1 of 2)
The root of the class hierarchy
Every class

Слайд 10Class Object (2 of 2)
equals(Object obj) - indicates whether some other object

Слайд 11Class Random
is used to generate a stream of pseudorandom numbers
Random(long seed) -

Слайд 12Class Math (1 of 2)
Contains methods for performing basic numeric operations:

Слайд 13Class Math (2 of 2)
sqtr(double value)
exp(double value)
log(double value)
power(double value, double p)
sin(double

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3. Essential Java Classes 5. Some Useful Classes презентация

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Слайд 13. Essential Java Classes5. Some Useful Classes

Слайд 2Class System (1 of 2)contains several useful class fields and methodsit

Слайд 3Class System (2 of 2)exit(int status) - terminates the currently running Java

Слайд 4Class RuntimeAllows to interface with the environment in which the application

Слайд 5Example of String Command ExecutionRuntime r = Runtime.getRuntime(); try{

Слайд 6Class Propertiesrepresents a persistent set of properties as pairs of key-valuedetails

Слайд 7Configuration File Exampledbpassword=pass&word database=localhost dbuser=vmo*Infopulse training Center

Слайд 8Use Properties ExampleProperties applicationProps = new Properties();in = new FileInputStream("appProperties");applicationProps.load(in); in.close();

Слайд 9Class Object (1 of 2)The root of the class hierarchyEvery class

Слайд 10Class Object (2 of 2)equals(Object obj) - indicates whether some other object

Слайд 11Class Randomis used to generate a stream of pseudorandom numbersRandom(long seed) -

Слайд 12Class Math (1 of 2)Contains methods for performing basic numeric operations:

Слайд 13Class Math (2 of 2)sqtr(double value)exp(double value)log(double value)power(double value, double p)sin(double

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Слайд 13. Essential Java Classes
5. Some Useful Classes

Слайд 2Class System (1 of 2)
contains several useful class fields and methods
it

Слайд 3Class System (2 of 2)
exit(int status) - terminates the currently running Java

Слайд 4Class Runtime
Allows to interface with the environment in which the application

Слайд 5Example of String Command Execution
Runtime r = Runtime.getRuntime();
try{

Слайд 6Class Properties
represents a persistent set of properties as pairs of key-value
details

Слайд 7Configuration File Example
dbpassword=pass&word
database=localhost
dbuser=vmo

*
Infopulse training Center

Слайд 8Use Properties Example
Properties applicationProps = new Properties();
in = new FileInputStream("appProperties");
applicationProps.load(in);
in.close();

Слайд 9Class Object (1 of 2)
The root of the class hierarchy
Every class

Слайд 10Class Object (2 of 2)
equals(Object obj) - indicates whether some other object

Слайд 11Class Random
is used to generate a stream of pseudorandom numbers
Random(long seed) -

Слайд 12Class Math (1 of 2)
Contains methods for performing basic numeric operations:

Слайд 13Class Math (2 of 2)
sqtr(double value)
exp(double value)
log(double value)
power(double value, double p)
sin(double