Following are the various constructors provided by the StringBuffer class.S.N.Constructor & Description1StringBuffer()This constructs a string buffer with no characters in it and an initial capacity of 16 characters.2StringBuffer(CharSequence seq)This constructs a string buffer that contains the same characters as the specified CharSequence.3StringBuffer(int capacity)This constructs a string buffer with no characters in it and the specified initial capacity.4StringBuffer(String str)This constructs a string buffer initialized to the contents of the specified string.

To find whether a given string contains a number, convert it to a character array and find whether each character in the array is a digit using the isDigit() method of the Character class.ExampleLive Demopublic class ContainsExample {    public static void main(String args[]){       String sample = "krishna64";       char[] chars = sample.toCharArray();       StringBuilder sb = new StringBuilder();       for(char c : chars){          if(Character.isDigit(c)){             sb.append(c);          }       }       System.out.println(sb);    } }Output64

You can change the cases of the letters of a word using toUpperCase() and toLowerCase() methods.Split each word in the string using the split() method, change the first letter of each word to lower case and remaining letters to upper case.ExampleLive Demopublic class Sample{    public static void main(String args[]){       String sample = "Hello How are you";       String[] words = sample.split(" ");       String result = "";       for(String word:words){          String firstSub = word.substring(0, 1);          String secondSub = word.substring(1);          result = result+firstSub.toLowerCase()+secondSub.toUpperCase()+" ";       }       System.out.println(result);    } }OutputhELLO hOW aRE yOU

The java.lang.String.contains() method returns true if and only if this string contains the specified sequence of char values.ExampleLive Demopublic class Sample {    public static void main(String args[]){       String str = "Hello how are you welcome to tutorialspoint";       String test = "tutorialspoint";       Boolean bool = str.contains(test);       System.out.println(bool);    } }Outputtrue

StringBuffer class of the java.lang package provides reverse() method. This method returns a reverse sequence of the characters in the current String. Using this method you can reverse a string in Java.To reverse each word in a string you need to split the string, store it in an array of strings and reverse each word using the reverse() method of the StringBuffer class.ExampleLive Demoimport java.lang.*; public class StringBufferDemo {    public static void main(String[] args) {       StringBuffer buff = new StringBuffer("tutorials point");       System.out.println("buffer = " + buff);       // reverse characters of the ... Read More

StringBuffer provides a method with name reverse() one way to check for a palindrome isCreate a StringBuffer object by passing the required string as a parameter to the constructor.Reverse the contents of the object using the reverse() method.Convert the StringBuffer object to Sting using the toString() method.Now, compare the String and the reversed one, if true, the given string is a palindrome.ExampleLive Demopublic class StringPalindrome {    public static void main(String args[]) {       String myString = "anna";       StringBuffer buffer = new StringBuffer(myString);       buffer.reverse();       String data = buffer.toString();       ... Read More

One way to do it to convert both strings to lower or upper case using toLowerCase() or toUpperCase() methods and test.ExampleLive Demopublic class Sample {    public static void main(String args[]){       String str = "Hello how are you welcome to Tutorialspoint";       String test = "tutorialspoint";       Boolean bool = str.toLowerCase().contains(test.toLowerCase());       System.out.println(bool);    } }Outputtrue

The contains() method of String class returns true if and only if this string contains the specified sequence of char values.ExampleLive Demoimport java.lang.*; public class StringDemo {    public static void main(String[] args) {       String str1 = "tutorials point", str2 = "http://";       CharSequence cs1 = "int";       // string contains the specified sequence of char values       boolean retval = str1.contains(cs1);       System.out.println("Method returns : " + retval);       // string does not contain the specified sequence of char value       retval = str2.contains("_");       System.out.println("Methods returns: " + retval);    } }OutputMethod returns : true Methods returns: false

The compareTo() method compares the Number object that invoked the method to the argument. It is possible to compare Byte, Long, Integer, etc.However, two different types cannot be compared, both the argument and the Number object invoking the method should be of the same type.ExampleLive Demopublic class Test {    public static void main(String args[]) {       Integer x = 5;       System.out.println(x.compareTo(3));       System.out.println(x.compareTo(5));       System.out.println(x.compareTo(8));    } }Output1 0 -1

To find weather a string is rotation of another, concat the first string to itself twice and find weatherExample Live Demopublic class Sample {    public static void main(String args[]){       String str1 = "gala";       String str2 = "alag";       String s3 = str1+str1;       if(s3.contains(str2)) {          System.out.println("str1 is rotation of str2");       } else {          System.out.println("str1 is not rotation of str2");       }    } }