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PART 9 Number Methods

9.1 toString() Method

The method is used to get a String object representing the value of the Number

Object. If the method takes a primitive data type as an argument then the String object

representing the primitive data type value is return.

String toString(int i)

Example

public class Test{

public static void main(String args[]){

int x = 5;

int y = 3;

System.out.println(Integer.toString(x) + Integer.toString(y));

}

}

This produces following result:

53

9.2 parseInt(), parseDouble() Methods

This method is used to get the primitive data type of a certain String. parseXxx() is a

static method and can have one argument or two.

int parseInt(String s)

int parseInt(String s, int radix)

s -- This is a string representation of decimal.

radix -- (radix equals 10, 2, 8, or 16 respectively). Parses given string into

decimal, binary, octal, or hexadecimal format.

Example

public class Test{


int x =Integer.parseInt("9");

double c = Double.parseDouble("5");

int b = Integer.parseInt("A",16);

System.out.println(x);

System.out.println(c);

System.out.println(b);

}

}


9

5.0

10

9.3 Math Methods Math.abs() The method gives the absolute value of the argument.

public class Test{


Integer a = -8;

double d = -100;

float f = -90;

System.out.println(Math.abs(a));

System.out.println(Math.abs(d));

System.out.println(Math.abs(f));

}

}

Math.ceil()

The method ceil gives the smallest integer that is greater than or equal to the argument.

public class Test{


double d = -100.675;

float f = -90;

System.out.println(Math.ceil(d));

System.out.println(Math.ceil(f));

}

}

Math.floor() The method floor gives the largest integer that is less than or equal to the argument.

public class Test{


double d = -100.675;

float f = -90;

System.out.println(Math.floor(d));

System.out.println(Math.floor(f));

}

}

Math.round() The method round returns the closest long or int, as given by the methods return type.

public class Test{


double d = 100.675;

double e = 100.500;

float f = 100;

float g = 90f;

System.out.println(Math.round(d));

System.out.println(Math.round(e));

System.out.println(Math.round(f));

System.out.println(Math.round(g));

}

}

Math.min()

The method gives the smaller of the two arguments.

public class Test{


System.out.println(Math.min(12.123, 12.456));

System.out.println(Math.min(23.12, 23.0));

}

}

Math.max()

The method gives the maximum of the two arguments.

public class Test{


System.out.println(Math.max(12.123, 12.456));

System.out.println(Math.max(23.12, 23.0));

}

}

Math.exp() The method returns the base of the natural logarithms, e, to the power of the argument.

public class Test{


double x = 2;

System.out.println("e :" + Math.E);

System.out.println("e^2 :" +Math.exp(x));

}

}

Math.pow() The method returns the value of the first argument raised to the power of the second argument.

public class Test{


double x = 2;

double y = 3;

System.out.println(Math.pow(x, y));

}

}

Math.sqrt() The method returns the square root of the argument.

public class Test{


double x = 2;

System.out.println(Math.sqrt(x));

}

}

Math.sin() The method returns the sine of the specified double value.

public class Test{


double degrees = 45.0;

double radians = Math.toRadians(degrees);

System.out.println(Math.sin(radians));

}

}

Math.cos() The method returns the cosine of the specified double value.

public class Test{




System.out.println(Math.cos(radians));

}

}

Math.tan() The method returns the tangent of the specified double value.

public class Test{




System.out.println(Math.tan(radians));

}

}

Math.random() The method is used to generate a random number between 0.0 and 1.0. The range is: 0.0 =< Math.random < 1.0.

Different ranges can be achieved by using arithmetic.

public class Test{


System.out.println( Math.random() );

System.out.println( Math.random() );

}

}

PART 10 10. Character Class

Normally, when we work with characters, we use primitive data types char.

Example

char ch = 'a';

// Unicode for uppercase Greek omega character

char uniChar = '\u03A9';

However in development we come across situations were we need to use objects

instead of primitive data types. In-order to achieve this Java provides wrapper

classe Character for primitive data type char.

The Character class offers a number of useful class methods for manipulating

characters. You can create a Character object with the Character constructor:

Character ch = new Character('a');

10.1 Character Methods

Here is the list of the important instance methods that all the subclasses of the

Character class implement:

Methods with Description Example

isLetter()

Determines whether the

specified char value is a

letter.

public class Test {

public static void main(String args[]) {

System.out.println(Character.isLetter('c'));

System.out.println(Character.isLetter('5'));

}

}


true

false

isDigit()


specified char value is a digit.

public class Test {


System.out.println(Character.isDigit('c'));

System.out.println(Character.isDigit('5'));

}

}


false

true

isWhitespace()

The method determines

whether the specified char

value is a white space which

includes

space,

tab

new line.

public class Test{


System.out.println(Character.isWhitespace('c'));

System.out.println(Character.isWhitespace(' '));

System.out.println(Character.isWhitespace('\n'));

System.out.println(Character.isWhitespace('\t'));

}

}


false

true

true

true

isUpperCase()


specified char value is

uppercase.

public class Test{


System.out.println( Character.isUpperCase('c'));

System.out.println( Character.isUpperCase('C'));

System.out.println( Character.isUpperCase('\n'));

System.out.println( Character.isUpperCase('\t'));

}

}


false

true

false

http://www.tutorialspoint.com/java/character_isletter.htm

http://www.tutorialspoint.com/java/character_isdigit.htm

http://www.tutorialspoint.com/java/character_iswhitespace.htm

http://www.tutorialspoint.com/java/character_isuppercase.htm

false

isLowerCase()


specified char value is

lowercase.

public class Test{


System.out.println(Character.isLowerCase('c'));

System.out.println(Character.isLowerCase('C'));

System.out.println(Character.isLowerCase('\n'));

System.out.println(Character.isLowerCase('\t'));

}

}


true

false

false

false

toUpperCase()

Returns the uppercase form

of the specified char value.

public class Test{


System.out.println(Character.toUpperCase('c'));

System.out.println(Character.toUpperCase('C'));

}

}


C

C

toLowerCase()

Returns the lowercase form

of the specified char value.

public class Test{


System.out.println(Character.toLowerCase('c'));

System.out.println(Character.toLowerCase('C'));

}

}


c

c

toString()

Returns a String object

representing the specified

character valuethat is, a one-

character string.

public class Test{


System.out.println(Character.toString('c'));

System.out.println(Character.toString('C'));

}

}


c

C

http://www.tutorialspoint.com/java/character_islowercase.htm

http://www.tutorialspoint.com/java/character_touppercase.htm

http://www.tutorialspoint.com/java/character_tolowercase.htm

http://www.tutorialspoint.com/java/character_tostring.htm

PART 11 11. Strings

Strings, which are widely used in Java programming, are a sequence of characters. In

the Java programming language, strings are objects.

The Java platform provides the String class to create and manipulate strings.

11.1 Creating Strings

The most direct way to create a string is to write:

String greeting = "Hello world!";

Whenever it encounters a string literal in your code, the compiler creates a String

object with its value in this case, "Hello world!'.

As with any other object, you can create String objects by using the new keyword and

a constructor. The String class has eleven constructors that allow you to provide the

initial value of the string using different sources, such as an array of characters:

public class StringDemo{


char[] helloArray = { 'h', 'e', 'l', 'l', 'o', '.'};

String helloString = new String(helloArray);

System.out.println( helloString );

}

}

This would produce following result:

hello

11.2 String Length

Methods used to obtain information about an object are known as accessor methods.

One accessor method that you can use with strings is the length() method, which

returns the number of characters contained in the string object.

After the following two lines of code have been executed, len equals 17:

public class StringDemo {


String palindrome = "Dot saw I was Tod";

int len = palindrome.length();

System.out.println( "String Length is : " + len );

}

}


String Length is : 17

11.3 Concatenating Strings

The String class includes a method for concatenating two strings:

string1.concat(string2);

This returns a new string that is string1 with string2 added to it at the end. You can

also use the concat() method with string literals, as in:

"My name is ".concat("Zara");

Strings are more commonly concatenated with the + operator, as in:

"Hello," + " world" + "!"

which results in:

"Hello, world!"

Let us look at the followinge example:

public class StringDemo {


String string1 = "saw I was ";

System.out.println("Dot " + string1 + "Tod");

}

}


Dot saw I was Tod

11.4 String Methods

Methods with Description Example

char charAt(int index)

Returns the character at the specified

index. The string indexes start from zero.

public class Test {


String s = "Strings are immutable";

char result = s.charAt(8);

System.out.println(result);

}

}


a

int compareTo(Object o)

Compares this String to another Object.

The value 0 if the argument is a string

lexicographically equal to this string; a

value less than 0 if the argument is a string

lexicographically greater than this string;

and a value greater than 0 if the argument

is a string lexicographically less than this

string.

public class Test {


String str1 = "Strings are immutable";

String str2 = "Strings are immutable";

String str3 = "Integers are not immutable";

int result = str1.compareTo( str2 );


result = str2.compareTo( str3 );


result = str3.compareTo( str1 );


}

}


0

10

-10

http://www.tutorialspoint.com/java/java_string_charat.htm

http://www.tutorialspoint.com/java/java_string_compareto.htm

int compareToIgnoreCase(String str)

Compares two strings lexicographically,

ignoring case differences.

public class Test {


String str1 = "Maltepe";

String str2 = "maltepe";

int result = str1.compareTo(str2);


result = str1.compareToIgnoreCase(str2);


}

}


-32

0

String concat(String str)

This method appends one String to the end

of another.

public class Test {


String s = "Strings are immutable";

s = s.concat(" all the time");

System.out.println(s);

}

}


Strings are immutable all the time

boolean endsWith(String suffix)

Tests if this string ends with the specified

suffix.

public class Test{


String Str = new String("This is immutable");

boolean retVal;

retVal = Str.endsWith( "immutable" );

System.out.println(retVal );

retVal = Str.endsWith( "immu" );

System.out.println(retVal );

}

}


true

false

boolean equals(Object anObject)

Compares this string to the specified

object.

public class Test {


String Str1 = new String("maltepe");

String Str2 = Str1;

String Str3 = new String("maltepe");

boolean retVal;

http://www.tutorialspoint.com/java/java_string_comparetoignorecase.htm

http://www.tutorialspoint.com/java/java_string_concat.htm

http://www.tutorialspoint.com/java/java_string_endswith.htm

http://www.tutorialspoint.com/java/java_string_equals.htm

retVal = Str1.equals( Str2 );

System.out.println("Returned = " + retVal );

retVal = Str1.equals( Str3 );


}

}


Returned = true

Returned = true

boolean equalsIgnoreCase(String

anotherString)

Compares this String to another String,

ignoring case considerations.

Modify the example given in the equals method description as shown

below.

String Str4 = new String("Maltepe");

retVal = Str1.equalsIgnoreCase( Str4 );


int length()

Returns the length of this string. public class Test{


String Str2 = new String("Tutorials" );

System.out.print("String Length :" );

System.out.println(Str2.length());

}

}


String Length :9

String replace(char oldChar, char

newChar)

Returns a new string resulting from

replacing all occurrences of oldChar in this

string with newChar.

public class Test{


String Str =new String("Maltepe University");

System.out.print("Return Value :" );

System.out.println(Str.replace('e', 'i'));

}

}


Return Value :Maltipi Univirsity

String toLowerCase()

Converts all of the characters in this String

to lower case using the rules of the default

locale.

public class Test{


String Str =new String("Maltepe University");

System.out.print("Return Value :");

System.out.println(Str.toLowerCase());

}

}


Return Value :maltepe university

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http://www.tutorialspoint.com/java/java_string_equalsignorecase.htm

http://www.tutorialspoint.com/java/java_string_length.htm

http://www.tutorialspoint.com/java/java_string_replace.htm

http://www.tutorialspoint.com/java/java_string_replace.htm

http://www.tutorialspoint.com/java/java_string_tolowercase.htm

String toLowerCase(Locale locale)


to lower case using the rules of the given

Locale.

public class Test{


String Str = “ILLAKI”;

System.out.println(Str.toLowerCase(new Locale("en")));

System.out.println(Str.toLowerCase());

}

}


illaki

ıllakı

String toUpperCase()


to upper case using the rules of the default

locale.

public class Test{


String Str = new String("Welcome to Java");


System.out.println(Str.toUpperCase() );

}

}


Return Value :WELCOME TO JAVA

String toUpperCase(Locale locale)


to upper case using the rules of the given

Locale.

public class Test{


String Str = “illaki”;

System.out.println(Str.toUpperCase(new Locale("en")));

System.out.println(Str.toUpperCase());

}

}


ILLAKI

İLLAKİ

String trim()

Returns a copy of the string, with leading

and trailing whitespace omitted.

public class Test{


String Str = new String(" Welcome to

Tutorials ");


System.out.println(Str.trim() );

}

}


Return Value :Welcome to Tutorials

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http://www.tutorialspoint.com/java/java_string_touppercase.htm

http://www.tutorialspoint.com/java/java_string_trim.htm

11.4.1 indexOf()

This method has following different variants:

public int indexOf(int ch): Returns the index within this string of the first

occurrence of the specified character or -1 if the character does not occur.

public int indexOf(int ch, int fromIndex): Returns the index within this string

of the first occurrence of the specified character, starting the search at the

specified index or -1 if the character does not occur.

int indexOf(String str): Returns the index within this string of the first

occurrence of the specified substring. If it does not occur as a substring, -1 is

returned.

int indexOf(String str, int fromIndex): Returns the index within this string of

the first occurrence of the specified substring, starting at the specified index. If

it does not occur, -1 is returned.

Here is the syntax of this method:

public int indexOf(int ch )

public int indexOf(int ch, int fromIndex)

int indexOf(String str)

int indexOf(String str, int fromIndex)

Here is the detail of parameters:

ch -- a character.

fromIndex -- the index to start the search from.

str -- a string.

Example

public class Test {


String Str = new String("Welcome to Tutorials about Java");

String SubStr1 = new String("Tutorials");

String SubStr2 = new String("Sutorials");

System.out.print("Found Index :" );

System.out.println(Str.indexOf( 'o' ));


System.out.println(Str.indexOf( 'o', 5 ));


System.out.println( Str.indexOf( SubStr1 ));


System.out.println( Str.indexOf( SubStr1, 15 ));


System.out.println(Str.indexOf( SubStr2 ));

}

}


Found Index :4

Found Index :9

Found Index :11

Found Index :-1

Found Index :-1

11.4.2 split()

This method has two variants and splits this string around matches of the given

regular expression.


public String[] split(String regex, int limit)

public String[] split(String regex)


regex -- the delimiting regular expression.

limit -- the result threshold which means how many strings to be returned.

Example

public class Test{


String Str = new String("Jim-Jack-Marry-David");

System.out.println("Return Value :" );

for (String retval: Str.split("-", 2)){

System.out.println(retval);

}

System.out.println("");




}





}



for (String retval: Str.split("-")){


}

}

}


Return Value :

Jim

Jack-Marry-David

Return Value :

Jim

Jack

Marry-David

Return Value :

Jim

Jack

Marry

David

Return Value :

Jim

Jack

Marry

David

11.4.3 startsWith()

This method has two variants and tests if a string starts with the specified prefix

beginning a specified index or by default at the beginning.


public boolean startsWith(String prefix, int toffset)

public boolean startsWith(String prefix)


prefix -- the prefix to be matched.

toffset -- where to begin looking in the string.

Example

import java.io.*;

public class Test{


String Str = new String("Welcome to Tutorials");


System.out.println(Str.startsWith("Welcome") );


System.out.println(Str.startsWith("Tutorials") );


System.out.println(Str.startsWith("Tutorials", 11) );

}

}


Return Value :true

Return Value :false

Return Value :true

11.4.3 subSequence()

This method returns a new character sequence that is a subsequence of this

sequence.


public CharSequence subSequence(int beginIndex, int endIndex)


beginIndex -- the begin index, inclusive.

endIndex -- the end index, exclusive.

Example public class Test{


String Str = new String("Welcome to Tutorials");


System.out.println(Str.subSequence(0, 10) );


System.out.println(Str.subSequence(10, 15) );

}

}


Return Value :Welcome to

Return Value : Tuto

PART 12 12. Arrays

Java provides a data structure, the array, which stores a fixed-size sequential

collection of elements of the same type. An array is used to store a collection of data,

but it is often more useful to think of an array as a collection of variables of the same

type.

Instead of declaring individual variables, such as number0, number1, ..., and

number99, you declare one array variable such as numbers and use numbers[0],

numbers[1], and ..., numbers[99] to represent individual variables.

12.1 Declaring Array Variables

To use an array in a program, you must declare a variable to reference the array, and

you must specify the type of array the variable can reference. Here is the syntax for

declaring an array variable:

double[] myList; // preferred way.

or

double myList[]; // works but not preferred way,

// comes from the C/C++ language and was adopted in Java to accommodate C/C++ programmers.

12.2 Creating Arrays

You can create an array by using the new operator with the following syntax:

Following statement declares an array variable, myList, creates an array of 10

elements of double type, and assigns its reference to myList.:

double[] myList = new double[10];

Following picture represents array myList. Here myList holds ten double values and

the indices are from 0 to 9.

12.3 Processing Arrays

When processing array elements, we often use either for loop or foreach loop

because all of the elements in an array are of the same type and the size of the array

is known.

Example

Here is a complete example of showing how to create, initialize and process arrays:

public class TestArray {

public static void main(String[] args) {

double[] myList = {1.9, 2.9, 3.4, 3.5};

// Print all the array elements

for (int i = 0; i < myList.length; i++) {

System.out.println(myList[i] + " ");

}

// Summing all elements

double total = 0;


total += myList[i];

}

System.out.println("Total is " + total);

// Finding the largest element

double max = myList[0];


if (myList[i] > max) max = myList[i];

}

System.out.println("Max is " + max);

}

}


1.9

2.9

3.4

3.5

Total is 11.7

Max is 3.5

12.4 The foreach Loops

JDK 1.5 introduced a new for loop, known as foreach loop or enhanced for loop,

which enables you to traverse the complete array sequentially without using an index

variable.

Example

The following code displays all the elements in the array myList:

public class TestArray {


double[] myList = {1.9, 2.9, 3.4, 3.5};

// Print all the array elements

for (double element: myList) {

System.out.println(element);

}

}

}


1.9

2.9

3.4

3.5

12.5 Passing Arrays to Methods

Just as you can pass primitive type values to methods, you can also pass arrays to

methods. For example, the following method displays the elements in an int array:

public static void printArray(int[] array) {

for (int i = 0; i < array.length; i++) {

System.out.print(array[i] + " ");

}

}

You can invoke it by passing an array. For example, the following statement invokes

the printArray method to display 3, 1, 2, 6, 4, and 2:

printArray(new int[]{3, 1, 2, 6, 4, 2});

12.6 sort() and binarySearch()

import java.util.Arrays;

public class ArrayDemo {


// initializing unsorted int array

int[] intArr = {30,20,5,12,55};

// sorting array

Arrays.sort(intArr);

// let us print all the elements available in list

System.out.println("The sorted int array is:");

for (int number : intArr) {

System.out.println("Number = " + number);

}

// entering the value to be searched

int searchVal = 12;

int retVal = Arrays.binarySearch(intArr,searchVal);

System.out.println("The index of element 12 is : " + retVal);

}

}

Let us compile and run the above program, this will produce the following result:

The sorted int array is:

Number = 5

Number = 12

Number = 20

Number = 30

Number = 55

The index of element 12 is : 1

part 9 - e-tahtam.comturgaybilgin/2012-2013-bahar/yzm... · system.out.println(math.ceil(f)); } }...

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