13.ARRAYS 14.WRAPPER CLASSES 15.STRINGS 16.STRING BUFFER/BUILDER 17.STRING TOKENIZER
ARRAYS: ******* Arrays has a some difference from c and cpp arrays.we have to create memory and size of the array.Array is a group of similar data items that share a common name.A particular value is indicated by writing a number called index or subscript. ex: num[10] 1.single dimensional 2.multi dimensional one dimensional array: A list of items can be given one variable name using only one subscript and such a variable is called a single subscripted variable or a one dimensional array. it is different from c.why because in c we should give the array size at the time of declaration.and it does not require the special memory creation but in java we have to declare the array without size and we have to create memoyr for that array. ex: int no[]; int[] no; no[]=new int[5];//creation of array and memory also int no[]={34,34,34,34};//initilization 'length' is a predifined variabe it used for knowig the lengtn of the array. int a=no.length; 2two dimensional array: A list of items can be given one variable name using two subscript and such a variable is called a multi subscripted variable or a multi dimensional array. int no[][]={ {34,354,45},{34,34,83},{34,88,93} }//intialization int no[0][0]=34; int no[1][1]=34; int no[2][2]=88; int no[][]=new int[3][3];// creation of memory and declaration; WRAPER CLASSES: *************** In 'c' we have 'atoi','atof','atol','atod' to convert the types.wrapper is nothing but a 'new look'.sometimes you need to convert the primitive type to an object and string formatted to number values into it's primitives type and vice versa. so for this application java provides wrapper classes. All primitive types have their classes means an 'int' type has it's Integer class and 'float' type has 'Float' class and soon. These kind of classes are called wrapper .wrapper classes provides by java.Each primitives has it's own type wrapper class. These are Character,Byte,Short,Integer,Long,Float Double,Boolean. *These classes are final and static so they cannot be inherited.* Byte: -------- //constants static final byte MAX-VALUE static final byte MIN-VALUE //cnstructors Byte(byte value) Byte( String s) Integer: -------- //constants static final int MAX-VALUE static final int MIN-VALUE //CONSTRUCTORS Integer(int value) Integer(String str) //class methods static int parseInt(String str) note:the above constants and parser methods are avaliable in every wrapper class. //instance methods byte byteValue() short shortValue() int intValue() long longValue() float floatValue() double doubleValue() String toString() STRINGS: ******** This is a class in java.lang package. The String class represents character Arrays.All string literals in java programs,such as "abc" are implemented as instances of this class. Strings are constants,thier values cannot be changed after they are created. String buffers support mutable strings. Because String objects are immutable they can be shared. for example: String str="abc"; is equalent to : char data[]={'a','b','c'}; string str=new String(data); The class string includes methods for examining individual characters of the sequence,for comparing strings,for extracting sub strings, and for creating a copy of a string with all characters translated to uppercase or to lowercase. The java provides special for the string concatnation operator(+) ,and for conversion of objects to strings.String concatenation is implemented througe the StringBuffer class and its append method. --------------- methods: public int length()// to get the length of string public char charAt(index)//to get the character public boolean equals(Object anObject) public equalsIgnoreCase(String anotherstring) public int compareTo(String anotherstring) public boolean startsWith(String prefix) public boolean endsWith(String suffix) public indexOf(int ch) public int lastIndexOf(int ch)// check public int indexOf(String str) public lastIndexOf(String str) public String subString(int beginindex) public String concat(String str) public String replace(char oldchar,char newchar) public String toLowerCase() public String toUpperCase() public String trim() ---------------- these are methods provided by java to perform operation on strings but one thing we have to remember i.e., after performing operations it returns new string.it does not change the originol string.it wastes the memory for new strings. STRING BUFFER/BUILDER: ********************** String buffer is as same as String class but it has more functionality and more flexibility available in java.lang package. It can be extended with some memory every time.when user try to store more strings content into object. constructors: StringBuffer()//default with size 16 bytes StringBuffer(int size)// size can be mentioned StrngBuffer(String str)//with string object methods: int length()//string length int capacity()// capacity of buffer char charAt(int where)// character of given position void setCharAt(int where,char ch)//replace old char with new StringBuffer append(String str)//to add more content StringBuffer insert(int where,String str)//t insert String in given pos StringBuffer reverse()//to reverse StringBuffer delete(int startpos,int endposi)//to delete text StringBuffer deleteCharAt(int location)//to remove character StringBuffer replace(int startpos,int endpos,String str) String subString(int substring) String subString(int startpos,int endposi) PROGRAM: import java.lang.*; class stringBufer { public static void main(String args[]) { String str="one two three four five"; StringBuffer sb=new StringBuffer(str); System.out.println("\n\n\n\t"+sb.capacity()+"\n\n\n\t"+sb.length()+sb); } } STRINGTOKENIZER: **************** StringTokenizer is a particular class availabel in java.util package. to divide a long length string into words are called 'tokens'.for this dividing the input string should have the delimiters like characters,generally ' '(space) or, newline(\n) or carrigeReturnwords(\r) etc....... default delimiter is space. class: java.util.StringTokenizer constructors: StringTokenizer(String str)// default delimiter is taken SrringTokenizer(String str,String delimiter)//can specify delimiter SrringTokenizer(String str,String delimiter,boolean value)//value denotes it consider delimiter as token methods: int countTokens()//number of tokens boolean hasMoreTokens()//return true if more tokens exits Object nextElement()//return next token as objefct String nextElement()//return next token as string String nextToken(String delimiters//to return next token and can set new dekimiters program: import java.lang.*; import java.util.*; class StringTokenizerTest { public static void main(String args[]) { String line="one two three four five"; line+="six seven eight nine ten"; StringTokenizer stk=new StringTokenizer(line); //StringTokenizer stk=new StringTokenizer(line,","); //StringTokenizer stk=new StringTokenizer(line,",",true); while(stk.hasMoreTokens()) { System.out.println("\n\ttotaltokens are "+stk.countTokens()); System.out.println("\t"+stk.nextToken()); } } }
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