Convert String to long in Java – Methods and Examples

Converting a String to a primitive long or a Long object in Java is a common task, especially when processing numeric input from the user, reading values from files, or parsing network responses. Java provides standard APIs that perform this conversion reliably with built-in error handling.

In this tutorial you will learn how to convert a Java String to the long type and the Long wrapper class in a safe, efficient way.

When You Need to Convert a String to long

Typical scenarios include:

• Parsing numerical IDs entered as text
• Reading numeric values from configuration or properties
• Processing numerical input in command-line, GUI, or web applications

Method 1: Using Long.parseLong(String)

Long.parseLong() converts a numeric string directly into a primitive long. This is the simplest and most common method.

Example

String numberStr = "1234567890";
long result = Long.parseLong(numberStr);
System.out.println("Converted long: " + result);

Notes

• Accepts only valid numeric representations
• Throws NumberFormatException if the string contains non-digit characters

Method 2: Using Long.valueOf(String)

Long.valueOf() returns a Long object rather than a primitive. It is useful when working with collections or APIs that expect wrapper types.

Example

String numberStr = "9876543210";
Long resultObj = Long.valueOf(numberStr);
long primitive = resultObj.longValue();
System.out.println("Converted Long object: " + resultObj);

Notes

• Internally uses Long.parseLong() and wraps the result
• Preferred when you need an object rather than a primitive

Handling Invalid Input Safely

When parsing user input or external data, always catch exceptions to avoid runtime crashes.

Example with Exception Handling

String input = "12ab34";

try {
    long value = Long.parseLong(input);
    System.out.println("Parsed value: " + value);
} catch (NumberFormatException e) {
    System.err.println("Invalid number: " + input);
}

Best Practices

• Validate input before parsing when possible
• Provide user-friendly error messages or fallbacks
• Avoid parsing unchecked strings without try/catch

Converting With a Default Value

To avoid exceptions and provide a default when parsing fails:

public static long toLongOrDefault(String str, long defaultValue) {
    try {
        return Long.parseLong(str);
    } catch (NumberFormatException e) {
        return defaultValue;
    }
}

// Usage
long val = toLongOrDefault("abc", 0L);

This pattern is useful in configuration parsing and batch processing.

Converting a String with Radix/Base

If you have numeric strings in non-decimal formats (e.g., hex), use:

String hexStr = "1A3F";
long hexValue = Long.parseLong(hexStr, 16);
System.out.println("Hex value: " + hexValue);

This supports bases from 2 to 36.

Avoiding NullPointerException

Always check for null before conversion:

String str = null;

if (str != null) {
    long val = Long.parseLong(str);
} else {
    // handle null value
}

Passing a null string to parseLong() causes NullPointerException.

Summary of Methods

Best Practices (Senior Engineering Insight)

• Always guard parsing with try/catch for robust applications
• Use helper methods for repeated parsing logic
• Validate input formats where possible before conversion
• Avoid parsing unchecked external input directly in business logic

These practices help prevent unhandled exceptions and improve application stability.