All the important string methods in Java
What is a String?
Strings are a bundle of different characters that are normally used in Java programming language. Strings are regarded as objects in the Java programming language.
“String” is a Java platform class that allows you to construct and handle strings.
Creating String:
The normal way of creating a String in Java is to simply write:
String s = “Hello World”;
The compiler constructs a String object with the value "Hello world!" whenever it detects a string phrase in your code.
String objects cannot be made by using the new keyword and a function Object, just like any other object. The String class provides 11 constructors that allow you to set the string's initial value from a variety of sources, including an array of characters.
Another way of a creating String is:
String s = new String (“Hello World”);
Methods of String
Length():
The length of a string is the number of characters it holds. The length() function in Java calculates the number of characters in a String.
Example:
package codes;
import java.lang.String;
public class StringMethods {
public static void main(String[] args) {
String str = "Hello World";
System.out.println(str.length());
}
}
OUTPUT:
11
String to CharArray():
This technique is used to create a Character Array from all of the characters in a string. This is commonly used in string manipulation software.
Example:
public class StringMethods {
public static void main(String[] args) {
String str = "HELLO";
char[] chars = str.toCharArray();
System.out.println(chars);
for (int i= 0; i< chars.length; i++) {
System.out.println(chars[i]);
}
}
}
OUTPUT:
H
E
L
L
O
String charAt()
This method is used to extract a single character from a string of characters.
Syntax:
char charAt(int i);
The value of ‘i’ should not be negative and it should specify the location of a given String i.e. if a String length is 5, then the value of ‘i’ should be less than 5.
Example:
public class StringMethods {
public static void main(String[] args) {
String str = "HELLO WORLD";
System.out.println(str.charAt(0));
System.out.println(str.charAt(1));
System.out.println(str.charAt(3));
System.out.println(str.charAt(4));
System.out.println(str.charAt(6));
}
}
OUTPUT:
H
L
O
W
equals (Object obj):
This method returns a Boolean value, indicating if the comparing string matches or not.
Example:
public class EqualsSample{
public static void main(String args[]){
String s1="java";
String s2="java";
String s3="string";
System.out.println(s1.equals(s2));
System.out.println(s1.equals(s3));
}
}
Output:
True
False
compareTo(String certainString):
This is a Comparable interface method that the String class implements. It is used to compare a string to the one currently in use string. As a consequence of the comparison, the method returns a value of 0 or a positive or negative number.
- When both the strings are equal it returns 0.
- If string 1st is less than string 2nd it returns negative.
- If string 1st is greater than string 2nd it returns positive.
Example:
public class CompareToSample{
public static void main(String args[]){
String s1="string ";
String s2="string";
String s3="ring";
String s4="swing";
System.out.println(s1.compareTo(s2));
//0 because both are equal
System.out.println(s1.compareTo(s3));
//1 because "s" is 1 time greater than "r"
System.out.println(s1.compareTo(s4));
// -3 because "t" is 3 times lower than "w"
}
}
Output:
0
1
-3replace(char oldLetter, char newLetter) :
This method returns a new string in which the old character is replaced by the new character in all of the string's occurrences.
Example:
public class EqualsSample{
public static void main(String args[]){
String s1="swap";
String s2 = replace(“w”,”n”);
String contains():
This method is used to identify whether or not a substring belongs to the main String. The type of the return value is Boolean.
Example:
public class StringMethods {
public static void main(String[] args) {
String str = "helloworld";
String str1 = "hello";
String str2 = "java";
System.out.println("hello is a part of helloworld: "
str.contains(str1));
System.out.println("java is a part of helloworld: " + str.contains(str2));
}
}
OUTPUT:
hello is a part of helloworld: true
java is a part of helloworld: false
Java String split()
A split() method divides or separates a supplied String into several substrings separated by delimiters ("", " ", etc.).
Example:
public class StringMethods {
public static void main(String[] args) {
String str = "MyxyznamexyzisxyzJohn”
String[] split = str.split("xyz");
for (String obj: split) {
System.out.println(obj);
}
}
}
OUTPUT:
My
name
is
John
Java String indexOf():
This method is used to execute a search of the main String for a specified character or substring. Another often used approach is lastIndexOf().
To find the first occurrence of a character, use indexOf(). The lastIndexOf() function is used to find the character's last occurrence.
Example:
public class StringMethods {
public static void main(String[] args) {
String str = "Saket Saurav " + "performing a search";
System.out.println(str);
System.out.println("index of 'p' is " + str.indexOf('p'));
System.out.println("index of 'u' is " + str.indexOf('u'));
System.out.println("last index of 'S' is " + str.lastIndexOf('S'));
System.out.println("last index of 's' is " + str.lastIndexOf('s'));
}
}
OUTPUT:
Saket Saurav performing a search
index of ‘p’ is 13
index of ‘u’ is 8
last index of ‘S’ is 6
last index of ‘s’ is 26
String Reverse():
To reverse the input characters of a String, use the StringBuffer reverse() function.
Example:
public class StringMethods {
public static void main(String[] args) {
String str = "dlrowolleh";
StringBuffer sb = new StringBuffer(str);
sb.reverse();
System.out.println(sb);
}
}
OUTPUT:
HelloworldSubstring():
The Substring() method is normally used to give the substring of the main String by specifying the starting and the last index of that particular substring.
Example:
public class StringMethods {
public static void main(String[] args) {
String str = "tutorialsandexamples";
System.out.println(str.substring(0,8));
//It will start from 8th character and extract the substring till 12th character
}
}
OUTPUT:
tutorials