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How to Convert String to Int in Java? String to Integer Program

Java offers a multitude of tools and functionalities to manipulate data efficiently. One common operation is converting a string to integer in Java, a process essential for various applications. In this tutorial, we will explore the processes of converting strings to integers, shedding light on the significance of both strings and integers in programming.

Before diving into the Java string to int conversion process, it's crucial to comprehend the fundamental concepts:

What is String in Java?

String in Java is a sequence of characters that represents text. Strings can contain letters, numbers, symbols, and spaces. They are widely used for representing and manipulating textual data, making them an integral part of Java programming.

What is Integer?

An integer, on the other hand, is a whole number without a decimal point. Integers can be positive, negative, or zero. They are used for performing arithmetic operations and storing numerical values in a program.

Use Cases of String to Integer Conversion in Java

The need to convert strings to integers often arises in various programming scenarios:

1. User Input Processing:

When receiving user input, such as from a text field or command-line argument, it usually comes in the form of strings. Converting these inputs to integers allows you to perform numerical operations or validations.

2. Data Parsing:

Many data sources provide information in string format. Converting these strings to integers is essential when dealing with numeric data, such as reading from a CSV file or a database.

3. String-to-Integer Conversion Functions:

Java provides built-in methods and libraries for parsing and converting strings to integers. Understanding how to utilize these tools is crucial for efficient data manipulation.

In this tutorial, let’s gain a comprehensive understanding of string-to-integer conversion in Java and the confidence to apply this knowledge to your programming projects.

Convert String to Int in Java Using Integer.parseInt()

Here's a program on how to convert a string to integer in Java using the Integer.parseInt() method:

Code

public class StringToIntExample {
    public static void main(String[] args) {
        // A string containing a numerical value
        String numberString = "12345";

        // Using Integer.parseInt() to convert the string to an integer
        int integerValue = Integer.parseInt(numberString);

        // Display the converted integer
        System.out.println("Converted Integer: " + integerValue);
    }
}

Output

Converted Integer: 12345

Explanation

  • We start by declaring a string variable named numberString and assign it the value "12345". This string contains the numerical value that we want to convert to an integer.

  • We use the Integer.parseInt() method to convert the numberString into an integer. This method takes a string as input and returns the corresponding integer value.

  • The resulting integer value is stored in the integerValue variable.

  • Finally, we print the converted integer to the console using System.out.println().

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Convert String to Integer in Java Using Integer.valueOf()

Here's a Java program that shows how to convert a string to an integer using the Integer.valueOf() method:

Code

public class StringToIntExample {
    public static void main(String[] args) {
        // A string containing a numerical value
        String numberString = "67890";

        // Using Integer.valueOf() to convert the string to an integer
        Integer integerValue = Integer.valueOf(numberString);

        // Display the converted integer
        System.out.println("Converted Integer: " + integerValue);
    }
}

Output

Converted Integer: 67890

Explanation

  • We start by declaring a string variable named numberString and assign it the value "67890". This string contains the numerical value that we want to convert to an integer.

  • We use the Integer.valueOf() method to convert the numberString into an integer. This method takes a string as input and returns an Integer object representing the corresponding integer value.

  • The resulting Integer object is stored in the integerValue variable. Note that this method returns an Integer object rather than a primitive int.

  • Finally, we print the converted integer to the console using System.out.println().

Convert String to Int in Java Using Constructor of Integer

Here's a Java program to convert a string to an integer using the constructor of the Integer class (new Integer(string)):

Code

public class StringToIntExample {
    public static void main(String[] args) {
        // A string containing a numerical value
        String numberString = "98765";

        // Using the constructor of the Integer class to convert the string to an integer
        Integer integerValue = new Integer(numberString);

        // Display the converted integer
        System.out.println("Converted Integer: " + integerValue);
    }
}

Output

Converted Integer: 98765

Explanation

  • We start by declaring a string variable named numberString and assign it the value "98765". This string contains the numerical value that we want to convert to an integer.

  • We use the constructor of the Integer class to convert the numberString into an integer. When we create a new Integer object using new Integer(numberString), Java automatically parses the string and creates an Integer object representing the corresponding integer value.

  • The resulting Integer object is stored in the integerValue variable. Like the Integer.valueOf() method, this approach also returns an Integer object.

  • Finally, we print the converted integer to the console using System.out.println().