Java: Convert a given String to int, long, float and double

Last update on May 21 2025 12:50:12 (UTC/GMT +8 hours)

102. Convert String to Number Types

Write a Java program to convert a given string to int, long, floating and double.

Visual Presentation:

Sample Solution:

Java Code:

 // Define a class named Main
public class Main {
    
    // The main method, entry point of the program
    public static void main(String[] args) {
        // Define strings to convert
        String STR_TO_INT = "1323";
        String STR_TO_LONG = "13625478965325";
        String STR_TO_FLOAT = "25.135F";
        String STR_TO_DOUBLE = "21.25478254D";
        
        // Convert String to int/Integer
        System.out.println("Convert String to int/Integer:");
        Integer toInt1 = Integer.valueOf(STR_TO_INT);
        int toInt2 = Integer.parseInt(STR_TO_INT);
        System.out.println("\"" + STR_TO_INT + "\"" + " as int is "
                + toInt1 + " and as Integer is " + toInt2);
                
        // Convert String to long/Long
        System.out.println("\nConvert String to long/Long:");
        Long toLong1 = Long.valueOf(STR_TO_LONG);
        long toLong2 = Long.parseLong(STR_TO_LONG);
        System.out.println("\"" + STR_TO_LONG + "\"" + " as long is "
                + toLong1 + " and as Long is " + toLong2);
        
        // Convert String to float/Float
        System.out.println("\nConvert String to float/Float:");
        Float toFloat1 = Float.valueOf(STR_TO_FLOAT);
        float toFloat2 = Float.parseFloat(STR_TO_FLOAT);
        System.out.println("\"" + STR_TO_FLOAT + "\"" + " as float is "
                + toFloat1 + " and as Float is " + toFloat2);
                
        // Convert String to double/Double
        System.out.println("\nConvert String to double/Double:");
        Double toDouble1 = Double.valueOf(STR_TO_DOUBLE);
        double toDouble2 = Double.parseDouble(STR_TO_DOUBLE);
        System.out.println("\"" + STR_TO_DOUBLE + "\"" + " as double is "
                + toDouble1 + " and as Double is " + toDouble2);
    }
}

Sample Output:

Convert String to int/Integer:
"1323" as int is 1323 and as Integer is 1323

Convert String to long/Long:
"13625478965325" as long is 13625478965325 and as Long is 13625478965325

Convert String to float/Float:
"25.135F" as float is 25.135 and as Float is 25.135

Convert String to double/Double:
"21.25478254D" as double is 21.25478254 and as Double is 21.25478254
false

Flowchart:

For more Practice: Solve these Related Problems:

• Write a Java program to convert a numeric string to int, long, float, and double using appropriate parsing methods.
• Write a Java program to validate and convert a string into various primitive numeric types with error handling.
• Write a Java program to transform a string representation of a number into int, long, float, and double and display the results.
• Write a Java program to implement conversions from string to number types and manage potential NumberFormatExceptions.

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