Strings in Java

Last modified: Nov 19, 2022 by Atrowel

In the previous blog we learned about the Bitwise Operator. If you want to know more about the Bitwise Operators then visit Bitwise Operators in Java. In this blog, we will go through the basic concept of Strings in Java and its methods. In Java String is a sequence of characters i.e. the character array. There is no built-in type for string. Rather, the Java library contains a predefined class which is called String. String class is immutable meaning once created we cannot change it, if we change it, then it will create an entirely new String. In order to create a String there are two ways:

Using String Literal
Using new keyword

Using String Literal

String can be created using the literals

e.g

String stringMsg = "Welcome to String in Java Blog";

The string which will be written in double quotes will go to one of the two places i.e. String constant pool or heap. For example in the above code the string “Welcome to Strings in Java Blog” will be stored in the string constant pool. JVM will then check for the existence of the string, if the string exists then it will reference the instance of that string.

e.g

String stringMsg = "Welcome to Strings in Java Blog";
String stringMsg2 = "Welcome to Strings in Java Blog";

In the above example stringMsg contains a String "Welcome to Strings in Java Blog", so "Welcome to Strings in Java Blog" will be stored in string constant pool and stringMsg will be pointed to it. In the second line as the stringMsg2 has the same String, so here stringMsg2 will point to the same location in the String Constant Pool where "Welcome to Strings in Java Blog" is stored.

Using new keyword

String can be created using the new keyword

e.g

String stringMsg = new String ("Welcome to Strings in Java Blog");

Now here, JVM will create a new string object in the heap and will store the literal "Welcome to Strings in Java Blog" in a heap and the variable stringMsg will be pointing to the location where the string “Welcome to Strings in Java Blog” is placed.

Methods of String in Java

charAt()

If we want to know what is the character value for the particular index in the string then we can use charAt(). The index starts from 0 to n-1, just like array indexing.

Syntax

public char charAt(nt index);

e.g

public class CharAtEx {
  public static void main(String args[]) {
    String stringMsg = "Welcome to String in Java Blog";
    char charCount = stringMsg.charAt(11);
    System.out.println("Index of the specified Character = " + charCount);
  }
}

Output

Index of the specified Character = S

Here in the example we want to find out which character is at the 11th location then, the count will start from 0 and will end with n - 1. The string contains 30 characters including a blank space in the middle, so the last character value will be 29(n-1 i.e. 30 -1). We cannot give an index greater than the string length, otherwise it will return an exception StringIndexOutOfBoundsException.

e.g

public class CharAtEx {
  public static void main(String args[]) {
    String stringMsg = "Welcome to String in Java Blog";
    char charCount = atrowel.charAt(30); //This line will give an exception i.e. StringIndexOutOfBoundsException
    System.out.println("Index of the specified Character = " + charCount);
  }
}

Output

Exception in thread "main" java.lang.StringIndexOutOfBoundsException: String index out of range: 30...

compareTo()

compareTo() lexicographically compares two strings. The comparison is predicated on the Unicode value of every character within the strings. It compares the sequence of characters in the given string with the sequence of the characters in the current string. The comparison returns results as positive, negative or 0 value. If there is a comparison between two strings and, if the first string is smaller than the second string, then it returns a negative result, if the first string is greater than the second string then, it results as a positive number and if both the strings are equal then, it returns zero.

Syntax

public int compareTo(String string);

e.g

public class CompareToEx {
  public static void main(String args[]) {
    String stringMsg = "Java Shortkicks";
    String stringMsg2 = "Java Shortkicks";
    String stringMsg3 = "Javva Shortkicks";
    String stringMsg4 = "Java";
    System.out.println("Comparison of two Strings = " + stringMsg.compareTo(stringMsg2));
    System.out.println("Comparison of two Strings = " + stringMsg.compareTo(stringMsg3));
    System.out.println("Comparison of two Strings = " + stringMsg.compareTo(stringMsg4));
    System.out.println("Comparison of two Strings = " + stringMsg3.compareTo(stringMsg4));
  }
}

Output

Comparison of two Strings = 0
Comparison of two Strings = -21
Comparison of two Strings = 11
Comparison of two Strings = 21

concat()

The general meaning of concat is to add something. Same applies in Java too, concat() combines (concatenates) the string at the end of the specified string.

Syntax

public String concat(String string);

e.g

public class ConcatEx {
  public static void main(String args[]) {
    String strMsg = "Java";
    String strMsg2 = "Shortkicks";
    System.out.println("Concatenation of the String = " + strMsg.concat("Shortkicks"));
    System.out.println("Concatenation of the String = " + strMsg.concat(strMsg2));
  }
}

Output

Concatenation of the String = JavaShortkicks
Concatenation of the String = JavaShortkicks

contains()

contains() searches for the specific characters in the string and if the sequence of characters are found, then it returns true, else it returns false.

Syntax

public boolean contains(CharSequence string);

e.g

public class ContainsEx {
  public static void main(String args[]) {
    String strMsg = "Java Shortkicks is a e-learning platform";
    String strMsg2 = "Shortkicks";
    System.out.println("Result of searches for the sequence of characters in the String = " + strMsg.contains("Shortkicks"));
    System.out.println("Result of searches for the sequence of characters in the String = " + strMsg.contains("is a e-learning platform"));
    System.out.println("Result of searches for the sequence of characters in the String = " + strMsg.contains("is a"));
    System.out.println("Result of searches for the sequence of characters in the String = " + strMsg.contains("Atrowel"));
  }
}

Output

Result of searches for the sequence of characters in the String = true
Result of searches for the sequence of characters in the String = true
Result of searches for the sequence of characters in the String = true
Result of searches for the sequence of characters in the String = false

endsWith()

endsWith() checks whether the string ends with the given suffix, if it ends with the suffix which is mentioned then it returns true, otherwise it returns false.

Syntax

public boolean endsWith(String string);

e.g

public class EndsWithEx {
  public static void main(String args[]) {
    String strMsg = "Java Shortkicks is a e-learning platform";
    String strMsg2 = "Shortkicks";
    System.out.println("Result of endsWith() = " + strMsg.endsWith("platform"));
    System.out.println("Result of endsWith() = " + strMsg.endsWith("form"));
    System.out.println("Result of endsWith() = " + strMsg.endsWith("m"));
    System.out.println("Result of endsWith() = " + strMsg.endsWith("learning"));
  }
}

Output

Result of endsWith() = true
Result of endsWith() = true
Result of endsWith() = true
Result of endsWith() = false

equals()

equals() compares the two given strings on the basis of the content of the string, if the two given strings are equal then it returns true, otherwise it returns false.

Syntax

boolean equals(Object obj);

e.g

public class DevEqualsEx {
  public static void main(String args[]) {
    String strMsg = "Shortkicks";
    String strMsg2 = "Shortkicks";
    String strMsg3 = "SHORTKICKS";
    String strMsg4 = "Java";
    System.out.println("Result of equals() = " + strMsg.equals(strMsg2));
    System.out.println("Result of equals() = " + strMsg.equals(strMsg3));
    System.out.println("Result of equals() = " + strMsg.equals(strMsg4));
    System.out.println("Result of equals() = " + strMsg3.equals(strMsg));
  }
}

Output

Result of equals() = true
Result of equals() = false
Result of equals() = false
Result of equals() = false

equalsIgnoreCase()

It works the same as equals(), but the only difference is equals() doesn’t allow lowercase or uppercase, but in case of equalsIgnoreCase() it compares the content of the two strings irrespective of lowercase or uppercase. Just like equals(), equalsIgnoreCase() returns true if the string matches with the other string irrespective of lowercase or uppercase.

Syntax

public boolean equalsIgnoreCase(String string);

e.g

public class EqualsIgnoreCase {
  public static void main(String args[]) {
    String strMsg = "Shortkicks";
    String strMsg2 = "Shortkicks";
    String strMsg3 = "SHORTKICKS";
    String strMsg4 = "Java";
    System.out.println("Result of equalsIgnoreCase() = " + strMsg.equalsIgnoreCase(strMsg2));
    System.out.println("Result of equalsIgnoreCase() = " + strMsg.equalsIgnoreCase(strMsg3));
    System.out.println("Result of equalsIgnoreCase() = " + strMsg.equalsIgnoreCase(strMsg4));
    System.out.println("Result of equalsIgnoreCase() = " + strMsg3.equalsIgnoreCase(strMsg));
  }
}

Output

Result of equalsIgnoreCase() = true
Result of equalsIgnoreCase() = true
Result of equalsIgnoreCase() = false
Result of equalsIgnoreCase() = true

Strings in Java

Using String Literal

Using new keyword

Methods of String in Java

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