Java Number Class

Java provides a set of Number classes as part of the java.lang package, which serve as the base classes for numeric data types such as Integer, Double, Float, Long, Short, and Byte. These classes are all subclasses of the abstract Number class, which defines several methods for converting numeric values between different formats. In this tutorial, we will cover the basics of using Java Number classes, including some examples.

Instantiating Number classes:

You can create instances of the Number classes using their constructors or using the valueOf() static methods.

Example:

Integer i1 = new Integer(42);
Integer i2 = Integer.valueOf(42);

Double d1 = new Double(3.14);
Double d2 = Double.valueOf(3.14);

Converting between numeric types:

The Number class defines several methods for converting numeric values to different formats, such as intValue(), doubleValue(), floatValue(), longValue(), shortValue(), and byteValue(). These methods are available in all Number subclasses.

Example:

Double d = 3.14;
int i = d.intValue();
float f = d.floatValue();
long l = d.longValue();
short s = d.shortValue();
byte b = d.byteValue();

Parsing strings into numeric values:

The Number subclasses provide parseXXX() and valueOf() static methods for converting string representations of numbers into numeric values.

Example:

String intString = "42";
int i = Integer.parseInt(intString);
Integer integer = Integer.valueOf(intString);

String doubleString = "3.14";
double d = Double.parseDouble(doubleString);
Double dbl = Double.valueOf(doubleString);

Formatting numeric values as strings:

The Number subclasses provide toString() methods for converting numeric values into string representations. Additionally, you can use String.format() or java.text package classes such as NumberFormat, DecimalFormat, and ChoiceFormat for more advanced formatting.

Example:

int i = 42;
String intString = Integer.toString(i);

double d = 3.14;
String doubleString = Double.toString(d);

String formattedDouble = String.format("%.2f", d); // Output: "3.14"

Comparing numeric values:

Number classes implement the Comparable interface, which provides the compareTo() method for comparing numeric values. You can also use the equals() method to check if two Number objects have the same value.

Example:

Integer i1 = 42;
Integer i2 = 24;

int comparisonResult = i1.compareTo(i2); // Output: 1 (i1 > i2)
boolean isEqual = i1.equals(i2); // Output: false

This tutorial introduced the basics of using Java Number classes, including creating instances of Number classes, converting between numeric types, parsing strings into numeric values, formatting numeric values as strings, and comparing numeric values. These classes provide a convenient and flexible way to work with numeric data in Java, and understanding how to use them effectively will help you write cleaner and more efficient code.

Working with numbers in Java using Number class:
- Example of using the Number class to work with numbers:
```
Number num = 42.5;
int intValue = num.intValue(); // Converts to int
```
Conversion between Number and primitive types in Java:
- Converting between Number and primitive types:
```
Number num = 42.5;
double doubleValue = num.doubleValue(); // Converts to double
```

Parsing and formatting numbers with Java Number class:

Parsing and formatting numbers using NumberFormat:

NumberFormat formatter = NumberFormat.getInstance();
Number parsedNumber = formatter.parse("123.45");

Java NumberFormatException and Number class:
- NumberFormatException can occur when parsing strings to numbers if the string is not a valid numeric representation.
```
try {
    int result = Integer.parseInt("abc"); // Throws NumberFormatException
} catch (NumberFormatException e) {
    // Handle the exception
}
```
Use of Number class in Java collections:
- Number and its subclasses can be used in collections to store numeric values as objects:
```
List<Number> numbersList = new ArrayList<>();
numbersList.add(42);
numbersList.add(3.14);
```

Java Number class examples:

Examples of using the Number class:

Number num = 10.75;
System.out.println(num.intValue()); // Outputs 10