Write a java program to reverse a string?
|
public
class ReverseTheString
{
public
static void main(String[] args)
{
String
str = "MyJava";
//1.
Using StringBuffer Class
StringBuffer
sbf = new StringBuffer(str);
System.out.println(sbf.reverse());
//Output : avaJyM
//2.
Using iterative method
char[]
strArray = str.toCharArray();
for
(int i = strArray.length - 1; i >= 0; i--)
{
System.out.print(strArray[i]);
//Output : avaJyM
}
System.out.println();
//3.
Using Recursive Method
System.out.println(recursiveMethod(str));
//Output : avaJyM
}
//Recursive
method to reverse string
static
String recursiveMethod(String str)
{
if
((null == str) || (str.length() <= 1))
{
return
str;
}
return
recursiveMethod(str.substring(1)) + str.charAt(0);
}
}
|
Write a java program to remove all white spaces from a
string.? –
class
RemoveWhiteSpaces
{
public static void main(String[] args)
{
String str = " Core Java jsp servlets jdbc struts hibernate spring ";
//1. Using replaceAll() Method
String strWithoutSpace =
str.replaceAll("\\s", "");
System.out.println(strWithoutSpace); //Output :
CoreJavajspservletsjdbcstrutshibernatespring
//2. Without Using replaceAll() Method
char[] strArray = str.toCharArray();
StringBuffer sb = new StringBuffer();
for (int i = 0; i < strArray.length;
i++)
{
if( (strArray[i] != ' ') &&
(strArray[i] != '\t') )
{
sb.append(strArray[i]);
}
}
System.out.println(sb); //Output :
CoreJavajspservletsjdbcstrutshibernatespring
}
}
3) Write a java program to find the duplicate words and their
number of occurrences in a string?
class
CountDuplicateWords
{
public static void main(String[] args)
{
System.out.println("Enter the
string");
Scanner sc = new Scanner(System.in);
String s=sc.nextLine();
String[] words = s.split("
");
HashMap<String, Integer>
wordDuplicateCount = new HashMap<String, Integer>();
int count;
for (int i = 0; i < words.length;
i++)
{
count = 0;
for (int j = 0; j <
words.length; j++)
{
if(words[i].equalsIgnoreCase(words[j]))
{
count++;
}
}
if(count > 1)
{
wordDuplicateCount.put(words[i].toLowerCase(), count);
}
}
System.out.println(wordDuplicateCount);
}
}
4) Write a java program to count the number of words in a
string?
class CountTheWords
{
public static void main(String[]
args)
{
System.out.println("Enter
the string");
Scanner sc
= new Scanner(System.in);
String
s=sc.nextLine();
String[] words =
s.trim().split(" ");
System.out.println("Number
of words in the string = "+words.length);
}
}
Or
class
CountTheWords
{
public static void main(String[] args)
{
System.out.println("Enter the
string");
Scanner sc = new Scanner(System.in);
String s=sc.nextLine();
int count = 1;
for (int i = 0; i < s.length()-1;
i++)
{
if((s.charAt(i) == ' ') &&
(s.charAt(i+1) != ' '))
{
count++;
}
}
System.out.println("Number of
words in a string = "+count);
}
}
5) Write a java program to count total number of occurrences
of a given character in a string without using any loop?
class
CountCharacterOccurence
{
public static void main(String[] args)
{
String s = "Java is java again
java again";
char c = 'a';
int count = s.length() -
s.replace("a", "").length();
System.out.println("Number of
occurances of 'a' in "+s+" = "+count);
}
}
5) Write a java program to count the number of occurrences of
each character in a string?
class CountCharOccurence
{
public static void
main(String[] args)
{
String str =
"java is java again java again";
HashMap<Character, Integer> charCount = new HashMap<Character,
Integer>();
int count;
char[] strArray
= str.toCharArray();
for (int i = 0;
i < strArray.length; i++)
{
count = 0;
for (int j =
0; j < strArray.length; j++)
{
if(strArray[i] == strArray[j])
{
count++;
}
}
charCount.put(strArray[i],
count);
}
System.out.println(charCount);
}
}
6)Java program to check whether one string is rotation of
another string?
public class MainClass
{
public static void
main(String[] args)
{
String s1 =
"JavaJ2eeStrutsHibernate";
String s2 =
"StrutsHibernateJavaJ2ee";
//Step 1
if(s1.length()
!= s2.length())
{
System.out.println("s2 is not rotated version of s1");
}
else
{
//Step 2
String s3 =
s1 + s1;
//Step 3
if(s3.contains(s2))
{
System.out.println("s2 is a rotated version of s1");
}
else
{
System.out.println("s2 is not rotated version of s1");
}
}
}
}
Copying An Array In Java
public class ArraysInJava
{
public static void
main(String[] args)
{
int[] a = {12,
21, 0, 5, 7}; //Declaring and
initializing an array of ints
int[] b =
a; //copying array 'a' to
array 'b'
//Printing
elements of array 'b'
for (int i = 0;
i < b.length; i++)
{
System.out.println(b[i]);
}
a[2] = 56; //Changing value of 3rd element of array
'a'
System.out.println(b[2]);
//value of 3rd element of array 'b' also changes
b[4] = 100; //Changing value of 5th element of array
'b'
System.out.println(a[4]);
//value of 5th element of array 'a' also changes
}
}
1) Copying An Array
Using for Loop :
public class ArraysInJava
{
public static void main(String[]
args)
{
int[] a =
{12, 21, 0, 5, 7}; //Declaring and
initializing an array of ints
int[] b
= new int[a.length]; //Declaring
and instantiating another array of ints with same length
for (int i
= 0; i < a.length; i++)
{
b[i]
= a[i];
}
//Now changing
values of one array will not reflect in another array
a[2]
= 56; //Changing value of 3rd
element in array 'a'
System.out.println(b[2]); //value
of 3rd element in array 'b' will not change
b[4]
= 100; //Changing value of 5th element in
array 'b'
System.out.println(a[4]); //value
of 5th element in array 'a' will not change
}
}
2) Copying An Array Using copyOf() Method of
java.util.Array Class
public class ArraysInJava
{
public static void main(String[] args)
{
int[] a = {12, 21, 0, 5, 7};
//Declaring and initializing an array of ints
//creating a copy of array 'a' using copyOf() method of java.util.Arrays
class
int[] b = Arrays.copyOf(a, a.length);
//Printing elements of array 'b'
for (int i = 0; i < b.length; i++)
{
System.out.println(b[i]);
}
//Now changing values of one array will not reflect in other array
a[2] = 56; //Changing value
of 3rd element in array 'a'
System.out.println(b[2]);
//value of 3rd element in array 'b' will not change
b[4] = 100; //Changing value
of 5th element in array 'b'
System.out.println(a[4]);
//value of 5th element in array 'a' will not change
}
}
3) Copying An Array Using clone() Method :
public class ArraysInJava
{
public static void main(String[] args)
{
int[] a = {12, 21, 0, 5, 7};
//Declaring and initializing an array of ints
//creating a copy of array 'a' using clone() method
int[] b = a.clone();
//Printing elements of array 'b'
for (int i = 0; i < b.length; i++)
{
System.out.println(b[i]);
}
//Now changing values of one array will not reflect in other array
a[2] = 56; //Changing value
of 3rd element in array 'a'
System.out.println(b[2]);
//value of 3rd element in array 'b' will not change
b[4] = 100; //Changing value
of 5th element in array 'b'
System.out.println(a[4]);
//value of 5th element in array 'a' will not change
}
}
4) Copying An Array Using arraycopy() Method Of System Class :
-
public class ArraysInJava
{
public static void main(String[] args)
{
int[] a = {12, 21, 0, 5, 7};
//Declaring and initializing an array of ints
//Creating an array object of same length as array 'a'
int[] b = new int[a.length];
//creating a copy of array 'a' using arraycopy() method of System class
System.arraycopy(a, 0, b, 0, a.length);
//Printing elements of array 'b'
for (int i = 0; i < b.length; i++)
{
System.out.println(b[i]);
}
//Now changing values of one array will not reflect in other array
a[2] = 56; //Changing value
of 3rd element in array 'a'
System.out.println(b[2]);
//value of 3rd element in array 'b' will not change
b[4] = 100; //Changing value
of 5th element in array 'b'
System.out.println(a[4]);
//value of 5th element in array 'a' will not change
}
}
Write a java
program to find common elements between two arrays?
OR
Write a java
program to find intersection of two arrays?
1) Using Iterative Method
class
CommonElements
{
public static void main(String[] args)
{
String[] s1 = {"ONE",
"TWO", "THREE", "FOUR", "FIVE",
"FOUR"};
String[] s2 = {"THREE",
"FOUR", "FIVE", "SIX", "SEVEN",
"FOUR"};
HashSet<String> set = new
HashSet<String>();
for (int i = 0; i < s1.length; i++)
{
for (int j = 0; j < s2.length;
j++)
{
if(s1[i].equals(s2[j]))
{
set.add(s1[i]);
}
}
}
System.out.println(set); //OUTPUT : [THREE, FOUR, FIVE]
}
}
2) Using retainAll() Method :
class CommonElements
{
public static void main(String[] args)
{
Integer[] i1 = {1, 2, 3, 4, 5, 4};
Integer[] i2 = {3, 4, 5, 6, 7, 4};
HashSet<Integer> set1 = new HashSet<>(Arrays.asList(i1));
HashSet<Integer> set2 = new HashSet<>(Arrays.asList(i2));
set1.retainAll(set2);
System.out.println(set1);
//Output : [3, 4, 5]
}
}
How To Check The Equality Of Two Arrays In Java?
1) Iterative Method :
public class EqualityOfTwoArrays
{
public static void main(String[] args)
{
int[] arrayOne = {2, 5, 1, 7, 4};
int[] arrayTwo = {2, 5, 1, 7, 4};
boolean equalOrNot = true;
if(arrayOne.length == arrayTwo.length)
{
for (int i = 0; i < arrayOne.length; i++)
{
if(arrayOne[i] != arrayTwo[i])
{
equalOrNot = false;
}
}
}
else
{
equalOrNot = false;
}
if (equalOrNot)
{
System.out.println("Two Arrays Are Equal");
}
else
{
System.out.println("Two Arrays Are Not equal");
}
}
}
2) Using Arrays.equals() Method :
class EqualityOfTwoArrays
{
public static void main(String[] args)
{
String[] s1 = {"java", "j2ee", "struts",
"hibernate"};
String[] s2 = {"jsp", "spring", "jdbc",
"hibernate"};
String[] s3 = {"java", "j2ee", "struts",
"hibernate"};
System.out.println(Arrays.equals(s1, s2)); //Output : false
System.out.println(Arrays.equals(s1, s3)); //Output : true
}
}
class EqualityOfTwoArrays
{
public static void main(String[] args)
{
String[] s1 = {"java", "swings", "j2ee",
"struts", "jsp", "hibernate"};
String[] s2 = {"java", "struts", "j2ee",
"hibernate", "swings", "jsp"};
Arrays.sort(s1);
Arrays.sort(s2);
System.out.println(Arrays.equals(s1, s2)); //Output : true
}
}
3) Using Arrays.deepEquals() Method :
public class EqualityOfTwoArrays
{
public static void main(String[] args)
{
String[][] s1 = { {"java", "swings",
"j2ee" }, { "struts", "jsp",
"hibernate"} };
String[][] s2 = { {"java", "swings",
"j2ee" }, { "struts", "jsp",
"hibernate"} };
System.out.println(Arrays.deepEquals(s1, s2)); //Output : true
//Calling equals() method on same arrays will return false
System.out.println(Arrays.equals(s1, s2)); //Output : false
//That's why use deepEquals() method to compare multidimensional arrays
}
}
Write a java
program to find duplicate elements in an array.? –
class DuplicatesInArray
{
public static void main(String[] args)
{
String[] strArray = {"abc", "def", "mno",
"xyz", "pqr", "xyz"};
//1. Using Brute Force Method
for (int i = 0; i < strArray.length-1; i++)
{
for (int j = i+1; j < strArray.length; j++)
{
if( (strArray[i].equals(strArray[j])) && (i != j) )
{
System.out.println("Duplicate
Element is : "+strArray[i]);
}
}
}
//2. Using HashSet
HashSet<String> set = new HashSet<String>();
for (String arrayElement : strArray)
{
if(!set.add(arrayElement))
{
System.out.println("Duplicate Element is : "+arrayElement);
}
}
}
}
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