Java Coding Questions

We will write a logic, to reverse the string at first we will find out the length of the given string. After that, we will write a for loop and will iterate from the end extracting the character from the string.

And we will add the extracted character in some other variable say reverse variable. We will keep on concatenating the character in the reverse variable. To extract the character from the string we will use the charAt method

 Program:

publicclass reverseString {
public static void main(String[] args) {
Scanner sc=new Scanner(System.in);
System.out.println("Provide the String");
String str=sc.next();
String rev=" ";
int length= str.length();
for(int i=length-1; i>=0; i--)
{
rev=rev+str.charAt(i);
}
System.out.println("Reverse of String is:  "+  rev);
}
}

Logic 2

Using StringBuffer class. We will create one object of StringBuffer class and will pass the string value. Now we will directly use the reverse method to reverse the string.

public class reverseString {
public static void main(String[] args) {
Scanner sc=new Scanner(System.in);
System.out.println("Entr the String");
String str=sc.next();
StringBuffer sbf= new StringBuffer(str);
StringBuffer rev=sbf.reverse();
System.out.println("Reverste of String is  "   +  rev);
}
}

3. Write a java program for Swapping 2 String without using the 3rd temp variable.

package javaprograns;public class Swap_Two_string {
 public static void main(String[] agrs) {
 String a="Hello"; String b="World";
 System.out.println("Values of String before Swapping"); System.out.println("Value of a:  "+a); System.out.println("Value of b:  "+b);
 a=a+b; //HelloWorld
 b=a.substring(0, a.length()-b.length()); a=a.substring(b.length());
 System.out.println("Values of String after Swapping"); System.out.println("Value of a:  "+a); System.out.println("Value of b:  "+b);
}

}

4. Various operations on a given String

• Find out the length
• Find out a character at a given position
• Find out the index of a character
• How to compare 2 Strings
• Replace method
• Split Method
• Converting the String in upper case to lower case and vice versa

Above all are various operations on a string.

package javaprograns;
public class String_Operations {
 public static void main(String[] args) {
String str="Hello in the Java world";
String str2="Good Morning and ";
// length of the string
System.out.println("Length of str: "+ str.length());
//Printing a character at a position
System.out.println("Character at 5th position is : "+str.charAt(6));
// find the index of any character
 System.out.println("Index of a is : "+str.indexOf("a"));
 // find the index of any character, starting the count from somewhere and not from starting
System.out.println("index of a after 14:  " + str.indexOf("a",str.indexOf("a")+1));
// String comparison
System.out.println(str.equals(str2) );
// sub string
System.out.println(str.substring(3, 6));
// replace
System.out.println(str.replace(" ", ""));
//Upper case
 System.out.println(str.toLowerCase());
// split
String splitstring[]= str.split(" ");
 for(int i=0;i<str.length(); i++)
 {
 System.out.println(splitstring[i]);
 }
}
}

5. Remove special characters and junk characters from a String.

Removing special characters and junk characters from a string using regular expression and replace all method.

package javaprograns;
public class Remove_JunkChars_from_String {
 public static void main(String[] args) {
 String s1="@##@#@@$@$%%^helloworld@$@%%!";
 s1=s1.replaceAll(("[^a-zA-Z0-9]"), ""); // s1 is a immutable
 System.out.println(s1);
}
}

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