String Operations

String Operations :


Concatenation using '+'.


Position of First 'o' using indexOf().

Position of LastIndex of 'o' using lastIndexOf().

Getting Substring in a String using substring method substring(beginIndex , endIndex);

Example :


/**
 *
 */
package com.techyield.operationsinarray;

public class StringModification {

/**
* @param args
*/
public static void main(String[] args) {

String s1 = "Sunny";
s1+=" G";

System.out.println(s1);

System.out.println("The index of first n : "+s1.indexOf('n'));
System.out.println("The index of last n :"+s1.lastIndexOf('n'));

// Substring

System.out.println(s1.substring(2,7));
}

}

Output :

Sunny G

The index of first n : 2

The index of last n :3

nny G

Notes:

We should be aware of the time complexity of built in operations.

If the length of the string is N , the time complexity of both finding and substring operation is O(N).

Never forget the time complexity of the built-in operations into consideration when you are finding the time complexity of your solution.

String Immutable Or Mutable

Immutable means that we can't change the content of the String once it is initialized.

1. In C++ String is Mutable . Which means you can modify the String just like array.

2. In Java String is Immutable. Which will create problems so many problems , we can resolve with the help of converting String to CharArray or Using StringBuilder .

Testing on String By Modifying It :

/**
 *
 */
package com.techyield.operationsinarray;

/**
 * @author satyanarayanagokavarapu
 *
 */
public class StringModification {

/**
* @param args
*/
public static void main(String[] args) {

String s1 = "Sunny";

s1[4]=','; // It will show compile Time Error as This type of expression can be array type //can be resolved to String .

System.out.println(s1);

}

}

Introduction To String

String :

A String is an array of Unicode Characters. But like Array we can perform all the operations on String .

But there are some differences based on programming language.

Operations&Functions On Strings :

Compare Function :

String has its own compare function.

"==" Can be used in Java to compare whether the two objects are same but cannot be used to compare two Strings.

"==" Can be used in C++ to Compare Two Strings as it supports Operator Overloading.


Example :

package com.techyield.operationsinarray;

public class OperationsInString {

public static void main(String[] args) {

String s1 = "Hello World! Chitti Version 2.0";

// s2 is reference of s1

String s2 = s1;

// s3 is copy of s1

String s3 = new String(s1);

System.out.println("s1 is \""+s1+"\"");

System.out.println("s2 is "+s2);

System.out.println("s3 is "+s3);

// compare using ==

System.out.println("Compare Strings using \"==\"");

System.out.println("Comparing s1 and s2"+ (s1==s2));

System.out.println("Comparing s2 and s3 using \"==\""+ (s2==s3));

System.out.println("Comparing s1 and s3 using \"==\""+ (s1==s3));

// compare using equals method

System.out.println("Compare Strings using equals method");

System.out.println("Comparing s1 and s2"+ (s1.equals(s2)));

System.out.println("Comparing s2 and s3 using \"==\""+ (s2.equals(s3)));

System.out.println("Comparing s1 and s3 using \"==\""+ (s1.equals(s1)));

// compare using compareTo method

System.out.println("Compare Strings using compareTo method");

System.out.println("Comparing s1 and s2"+ (s1.compareTo(s2) == 0));

System.out.println("Comparing s2 and s3 using \"==\""+ (s2.compareTo(s3) == 0));

System.out.println("Comparing s1 and s3 using \"==\""+ (s1.compareTo(s1) == 0));

}

}

Introduction to 2D Array

Like in One Dimensional Array . Two Dimensional array also consists of sequence of elements.

But the elements can be laid in rectangular grid rather than a line.

We also have 2D Dynamic array Just as 1D Dynamic array https://techyield.blogspot.com/2019/06/introduction-to-dynamic-array.html

Let's take a look at an example of using a two-dimensional array:

package com.techyield.operationsinarray;

public class OperationsIn2Darray {

private static void printArray(int[][] a) {

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

         System.out.println(a[i]);

}

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

for(int k=0; a[i]!= null && k < a[i].length; k++) {

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

}

System.out.println();

}

}

public static void main(String[] args) {

System.out.println("Example I:");

int [][] a = new int[2][];

printArray(a);

System.out.println(" Example 2:");

int [][] b = new int[3][5];

printArray(b);

System.out.println("Example 3:");

b[0] = new int[3];

b[1] = new int[5];

printArray(b);

}

}

Introduction To Dynamic Array

In general Array has fixed capacity .  Array that we are talking about is linear array and we need to give size of the array when we initialize it  , which is wasteful and inconvenient sometimes.


Most programming languages offer built in dynamic array. Which is a random access list data structure with variable size .

We have ARRAYLIST in Java which is similar to Vector C++.

/**
 *
 */
package com.techyield.operationsinarray;

import java.util.ArrayList;
import java.util.Arrays;
import java.util.Collections;
import java.util.List;

class OperationsInDynamicArray {

/**
* @param args
*/
public static void main(String[] args) {
       
// Initialize
List<Integer> l1 = new ArrayList<>();
List<Integer> l2 ; // here l2 == null

// Cast an array to List
Integer[] array = {1,2,3,4,5,6,7,8};
l2 = new ArrayList<>(Arrays.asList(array));

// Make a copy

List<Integer> l3 = l2;  // another reference to l1
List<Integer> l4 = new ArrayList<>(l2); // make an actual copy of l2

// Length

System.out.println("The size of list is "+l2.size());

// Access Element
System.out.println("The first element in l2 is "+l2.get(0));

// Iterate the linkedList
System.out.println("The contents of l2 are : ");
for(Integer a : l2) {
System.out.println(a);
}
System.out.println(" Version2 ............");
for(int i =0 ; i < l2.size(); i++) {
System.out.println(" "+l2.get(i));
}
System.out.println();

// Modify the element
l2.set(0,5);
System.out.println("l2.get(0)"+l2.get(0));
// Modify the element
l2.set(0, -1);
System.out.println("l2.get(0)"+l2.get(0));
// here l3 refers to l2 so modifying l2 modifies l3
// Sort
Collections.sort(l2);
// Add a new element at the end of the ArrayList
l2.add(9);

l2.add(2,5);

// Remove an element

l2.remove(l2.size()-1);

for(int u : l2) {
System.out.println(u);
}




}

}

Introduction To Array

Array :

Array is an basic data structure used to store a collection of elements sequentially.

Elements in an array can be accessed randomly because elements in array can be identified by array index.

We have one dimensional array and multi-dimensional array.

One dimensional array is known as Linear array.

Example :

Here , we can access 2 as num[0] , 6 as num[3]

Operations in Array :

Initialize 

Length of an array 

Access an Element 

Iterate all the Elements 

Modify Elements

Sort

// Example :

package com.techyield.operationsinarray;

import java.util.Arrays;

public class OperationsinOneDimensionalArray {

public static void main(String[] args) {

//Intialize

int [] array1 = new int[5];

int [] array = {1,2,3,4,5,6};

// Getting Length

System.out.println("The Size of array1 is "+array1.length);

System.out.println("The Size of array2 is "+array.length);

// Access 4th element  in array2

System.out.println("The 4th element in array"+array[3]);

// Iterate all the elements in array

// First Version

System.out.println("Fetching elements using for loop");

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

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

}

System.out.println();

System.out.println("Fetching elements from array using forEach ");

for(int k : array) {

System.out.println(" "+k);

}

System.out.println();

// Modify Elements 

System.out.println("Modify 3rd ELement in array ");

array[2]= 9;

for(int p : array) {

System.out.println(" "+p);

}

System.out.println(" Sort the Elements");

// Sort the Elements

Arrays.sort(array);

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

System.out.println(" "+array[u]);

 

}

}

// Output :

The Size of array1 is 5

The Size of array2 is 6

The 4th element in array4

Fetching elements using for loop

 1

 2

 3

 4

 5

 6

Fetching elements from array using forEach 

 1

 2

 3

 4

 5

 6

Modify 3rd ELement in array 

 1

 2

 9

 4

 5

 6

 Sort the Elements

 1

 2

 4

 5

 6

 9

   

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