data type conversion in Java


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  1. In Java, data type conversion is a common operation that can be categorized into two types: implicit (automatic) conversion and explicit (manual) conversion.

    Implicit Conversion

    Implicit conversion, also known as automatic type conversion, is performed by the Java compiler when assigning a value of a smaller data type to a larger data type. This process is safe and does not lead to data loss. For example, converting an int to a long, or a float to a double.

    int myInt = 100;
    long myLong = myInt;  // Automatically converts the int to a long
    float myFloat = myLong;  // Automatically converts the long to a float

    Explicit Conversion

    Explicit conversion, or casting, is required when you need to convert a value from a larger data type to a smaller data type, or when converting between two types that are not compatible by default. This process can lead to data loss or precision loss, so it must be done with caution.

    To perform explicit conversion, you place the target type in parentheses in front of the value you wish to convert.

    double myDouble = 9.78;
    int myInt = (int) myDouble;  // Casts the double to an int

    This will truncate the decimal part, and myInt will have a value of 9.

    Special Cases

    • Converting between numeric types and String: You can convert a numeric type to a String either using the String.valueOf() method or concatenation with an empty String (""). To convert a String to a numeric type, you can use wrapper classes like Integer, Double, etc., with methods like parseInt(), parseDouble(), etc.
    // Numeric to String
    int num = 100;
    String numStr = String.valueOf(num);  // Method 1
    String numStr2 = num + "";  // Method 2
    // String to Numeric
    String value = "123";
    int number = Integer.parseInt(value);
    • Boxing and Unboxing: Converting primitive data types into their corresponding wrapper class objects is called boxing, and the reverse process is called unboxing.
    // Boxing
    int myInt = 500;
    Integer myInteger = myInt;  // Automatically converts the int to Integer
    // Unboxing
    Integer myInteger2 = new Integer(500);
    int myInt2 = myInteger2;  // Automatically converts the Integer to int


    Type conversion in Java is a powerful feature that needs to be used wisely to avoid data loss or precision loss. Implicit conversions are safe and automatic, but explicit conversions (casting) require careful consideration of the potential impact on data values.

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