String Handling methods and their working behaviors
Hello guys, This is me Sagar Sonawane and its my first blog over medium.com over technical concept,and this blog will be different from others, because in this blog we are going to discuss methods along with program and explanation, so today we are going to see how the methods work and where/when can use those methods in programming with example and explanation . so let’s get started!
Introduction to String
A String is a sequence of characters. A string is treated as an object. After creating a string object you can not change it. So that is why it is said that a string is immutable.
String Handling in Java
The string is a sequence of characters. We can call an array of characters a string.
Let see this example.
public class Main{
public static void main(String args[]){
char[] c={'j','a','v','a'};
String s1=new String(c);
String s2="java";
System.out.println(s1);
System.out.println(s2);
}
}Like the above example, character array c and string s2 are the same only. As we have already seen, we can define string using literal or using the new operator. String objects are immutable objects. You can perform operations over it without storing those values.
Now, let us explore how Java handles string with different examples.
1) String Length
String length is the number of characters in it. The string object has a predefined method available called length() to obtain no. of characters in it.
public class Main{
public static void main(String args[]){
String s1="java";
System.out.println(s1.length());
}
}Output:
4
String Modification
2) String Concatenation
Java has a “+” operator to attach more than one string or string with some other data type value. We can have multiple chains of operations by using the + operator.
As we can see in the below example, we can join a string with another string literal, another string variable, or another data type variable here, in this case, an integer.
public class Main{
public static void main(String args[]){
String s1="Java";
int i = 10;
System.out.println("Learn " + s1);
System.out.println(s1 + "Version :" + i);
}
}Output:
Learn Java
java version: 10
We can also use concat() method to join strings same as above example.
public class Main{
public static void main(String args[]){
String s1="Java";
String s2 = "Learn";
s2.concat(s1);
System.out.println(s2);
System.out.println(s2.concat(s1));
}
}Output:
Learn
LearnJava
Here you can see, even after concatenation operation, s2 object’s value is still the same. That is why we have termed that string objects are immutable. When we perform a concatenation operation, it will be a new object but the older object’s value won’t be changed.
Extraction
Java can extract substrings using the substring() method. Its general form is as below:
String substring(int startIndex, int endIndex)
Here, if we have omitted endIndex then, it will extract the substring from startIndex till the end of the string.
public class Main{
public static void main(String args[]){
String s1="Learn Java";
System.out.println(s1.substring(1));
System.out.println(s1.substring(1,5));
}
}Output:
earn Java
earn
Like 1st statement, if we omit endIndex, it will fetch from startIndex to the end of the string.
Replace
Java has a method called replace() to replace one character with another. The general form of replace() method is shown below:
String replace(char original, char replace)
Here, instead of one character we can also pass a string and replace it with another string. Below is shown..
public class Main{
public static void main(String args[]){
String s1="Learn Java in 10 days";
System.out.println(s1.replace('a','e'));
System.out.println(s1.replace("in","within"));
}
}Output:
Leern jeve in 10 deys
Learn java within 10 days
Trim
Java has a trim() method to remove extra white spaces from strings. It is very useful while processing user inputs.
public class Main{
public static void main(String args[]){
String s1=" Learn Java in 10 days ";
System.out.println(s1);
System.out.println(s1.trim());
}
}Output:
Learn Java in 10 days
Learn Java in 10 days
Here, you can see how trim() has worked. Method removed the blank spaces.
Case Conversion
Java has methods to convert the case of the strings.
String toUppercase()
String toUpperCase( )
These methods will convert the case of the whole string. These are very useful for user inputs where there will not be any consistency in which case the user will input their values. Non Alphabetic characters are not getting affected by these methods.
public class Main{
public static void main(String args[]){
String s1="Learn Java in 10 days";
System.out.println(s1);
System.out.println(s1.toUpperCase());
System.out.println(s1.toLowerCase());
}
}Output:
Learn Java in 10 days
LEARN JAVA IN 10 DAYS
learn java in 10 days
String Conversion
Java has a method called toString() to convert the object into a string object. So when we concat any objects, Java internally hit the toString() method to perform the operation and return the string object. Now, if we want to show an object as a string object, we can override the toString() object and return the information in whichever way we like.
Let us understand through the below example:
class employee
{
int empid;
String ename;
employee(int empid, String ename){
this.empid=empid;
this.ename=ename;
}
public String toString(){ //overriding the toString() method
return empid+" "+ename;
}
}
public class Main{
public static void main(String args[]){
employee e1=new employee(1001,"Sagar");
employee e2=new employee(1002,"Ganesh");
System.out.println(e1); //compiler writes e1.toString()
System.out.println(e2); //e2.toString
}
}Output:
1001 Sagar
1002 Ganesh
String Comparison
Java has the below methods to compare two strings or substrings. Let us understand their usage with examples.
equals() and equalsIgnoreCase()
These 2 methods returns true if both strings are same and false if not same.
public class Main{
public static void main(String []args){
String s1 = "Learn";
String s2 = "Java";
String s3 = "JAVASCRIPT";
System.out.println(s1.equals(s2));
System.out.println(s3.substring(0,4));
System.out.println(s2.equals(s3.substring(0,4)));
System.out.println(s2.equalsIgnoreCase(s3.substring(0,4)));
}
}Output:
false
JAVA
false
true
Here in this example, we can see the usage of equals() and equalsIgnoreCase() methods. It always returns a Boolean value.
This works the same as equals() method and returns true in the case of similar strings. The only difference here is that == compares references, not values.
public class Main{
public static void main(String []args){
String s1 = “Java”;
String s2 = “Java”;
String s3 = new String(“Java”);
System.out.println(s1==s2);
System.out.println(s2==s3);
}
}
Output:
true
false
Here == operator compares 2 object references and see whether those two refer to the same instances. If the same instance then it will return true else it will return false even if both objects have the same values in it.
startsWith() and endsWith()
startsWith() method is used in Java to check whether a string starts with some specific string.
endsWith() method is used in Java to check whether a string ends with some specific string.
Both these methods return a Boolean value and their general form is as below:
boolean startsWith(String s)
boolean endsWith(String s)
If string matched the criteria, the statement returns true else it returns false.
public class Main{
public static void main(String []args){
String s1 = "Learn Java";
System.out.println(s1.startsWith("Learn"));
System.out.println(s1.endsWith("Java"));
}
}Output:
true
true
I, hope guys you would have liked this article, will meet you on next blog .
thank you….
