String class
● The java.lang.String class provides a lot of methods to work on string. By the help of these methods, we can perform operations on string such as trimming, concatenating, converting, comparing, replacing strings etc.
● Java String is a powerful concept because everything is treated as a string if you submit any form in window based, web based or mobile application.
toUpperCase() and toLowerCase() method
● The java string toUpperCase() method converts this string into uppercase letter and string toLowerCase() method into lowercase letter.
Syntax:-
String toLowerCase()
String toUpperCase()
Example:-
String s="Sachin";
System.out.println(s.toUpperCase());//SACHIN
System.out.println(s.toLowerCase());//sachin
System.out.println(s);//Sachin(no change in original)
String trim() method
● The string trim() method eliminates white spaces before and after string.Syntax:-
String trim()
Example:-
String s=" Sachin ";
System.out.println(s);// Sachin
System.out.println(s.trim());//Sachin
String startsWith() and endsWith() method
● 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.Syntax:-
boolean startsWith(String prefix, int toffset)
boolean endsWith(String prefix, int toffset)
Example:-
String s="Sachin";
System.out.println(s.startsWith("Sa"));//true
System.out.println(s.endsWith("n"));//true
String charAt() method
● The string charAt() method returns a character at specified index.Syntax:-
char charAt(int index)
Example:-
String s="Sachin";
System.out.println(s.charAt(0));//S
System.out.println(s.charAt(3));//h
String length() method
● The string length() method returns length of the string. The length is equal to the number of 16-bit Unicode characters in the string.Syntax:-
int length()
Example:-
String s="Sachin";
System.out.println(s.length());//6
String valueOf() method
● The string valueOf() method converts given type such as int, long, float, double, boolean, char and char array into string.Syntax:-
String valueOf(double d)
Example:-
int a=10;
String s=String.valueOf(a);
System.out.println(s+10); //1010
String replace() method
● The string replace() method replaces all occurrence of first sequence of character with second sequence of character.
Syntax:-
String replace(char oldChar, char newChar)
Example:-
String s1="Java is a programming language. Java is a platform. Java is an Island.";
String replaceString=s1.replace("Java","Kava");//replaces all occurrences of "Java" to "Kava"
String substr() method
● This method has two variants and returns a new string that is a substring of this string. The substring begins with the character at the specified index and extends to the end of this string or up to endIndex – 1, if the second argument is given.Syntax:-
public String substring(int beginIndex, int endIndex)
Example:-
String Str = new String("Welcome to Java SY A"); System.out.println(Str.substring(10, 13) ); //Java
String compareTo() method
● This method compares two strings lexicographically.Syntax:-
int compareTo(String anotherString)
The value 0 if the argument is a string equal to this string; a value less than 0 if the argument is a string greater than this string; and a value greater than 0 if the argument is a string less than this string.
String str1 = "Strings are immutable";
String str2 = "Strings are immutable";
String str3 = "Integers are not immutable";
int result = str1.compareTo( str2 ); //0
System.out.println(result);
result = str2.compareTo( str3 ); //10
System.out.println(result);
result = str3.compareTo( str1 ); //-10
System.out.println(result);
String Buffer class
● The java.lang.StringBuffer class is a thread-safe, mutable sequence of characters. Following are the important points about StringBuffer:● A string buffer is like a String, but can be modified.
● It contains some particular sequence of characters, but the length and content of the sequence can be changed through certain method calls.
● They are safe for use by multiple threads.
● Every string buffer has a capacity.
StringBuffer.capacity() method
● The java.lang.StringBuffer.capacity() method returns the current capacity. The capacity is the amount of storage available for newly inserted characters, beyond which an allocation will occur.● Syntax: int capacity()
StringBuffer.append()
● The java.lang.StringBuffer.append(String str) method appends the specified string to this character sequence.● The characters of the String argument are appended, in order, increasing the length of this sequence by the length of the argument.
● If str is null, then the four characters "null" are appended.
● Syntax:-
StringBuffer append(String str)
StringBuffer.replace()
● The java.lang.StringBuffer.replace() method replaces the characters in a substring of this sequence with characters in the specified String.
● The substring begins at the specified start and extends to the character at index end - 1 or to the end of the sequence if no such character exists.
● First the characters in the substring are removed and then the specified String is inserted at start.
● Syntax:- StringBuffer replace(int start, int end, String str)
StringBuffer.reverse()
● The java.lang.StringBuffer.reverse() method causes this character sequence to be replaced by the reverse of the sequence.● Syntax:-StringBuffer reverse()
StringBuffer.charAt()
● The java.lang.StringBuffer.charAt() method returns the char value in this sequence at the specified index.● The first char value is at index 0, the next at index 1, and so on, as in array indexing.
● The index argument must be greater than or equal to 0, and less than the length of this sequence.
Syntax:- char charAt(int index)
StringBuffer.setCharAt()
● The java.lang.StringBuffer.setCharAt() method sets the character at the specified index to ch.
● This sequence is altered to represent a new character sequence that is identical to the old character sequence, except that it contains the character ch at position index.
● Syntax:-void setCharAt(int index, char ch)
NeXt Artical Related APPLET in Java
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