Type Casting and Promotion
Understanding how Java handles type conversion is essential for writing safe and predictable code. Java supports two main forms of type conversion between primitive types: implicit conversion (also called widening) and explicit conversion (also called narrowing). Implicit conversions happen automatically when you assign a value of a smaller data type to a larger one, such as assigning an int to a double. Explicit conversions require you to manually cast the value, usually because there is a risk of losing data, such as when converting a double to an int or an int to a byte.
When you assign a value from a smaller type to a larger type, Java performs the conversion automatically. This is safe because the larger type can represent all possible values of the smaller type. Assigning an int to a double does not lose information, since all int values can be represented as double values. This is known as widening conversion.
When assigning a value from a larger type to a smaller type, Java requires you to use an explicit cast. This is because the smaller type might not be able to represent all values of the larger type, which can lead to data loss or unexpected results. Casting a double to an int will truncate the decimal part, and casting an int to a byte can cause the value to wrap around if it is outside the range of a byte. This process is called narrowing conversion.
Main.java
1234567891011121314151617package com.example; public class Main { public static void main(String[] args) { int i = 150; double d = i; // Implicit widening conversion: int to double System.out.println("int to double: " + d); // 150.0 double d2 = 123.456; int i2 = (int) d2; // Explicit narrowing conversion: double to int System.out.println("double to int: " + i2); // 123 int i3 = 300; byte b = (byte) i3; // Explicit narrowing conversion: int to byte System.out.println("int to byte: " + b); // 44 (data loss due to overflow) } }
1. Which of the following primitive type conversions can be performed implicitly in Java?
2. What is the result of casting the value 9.99 (as a double) to an int in Java?
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Understanding how Java handles type conversion is essential for writing safe and predictable code. Java supports two main forms of type conversion between primitive types: implicit conversion (also called widening) and explicit conversion (also called narrowing). Implicit conversions happen automatically when you assign a value of a smaller data type to a larger one, such as assigning an int to a double. Explicit conversions require you to manually cast the value, usually because there is a risk of losing data, such as when converting a double to an int or an int to a byte.
When you assign a value from a smaller type to a larger type, Java performs the conversion automatically. This is safe because the larger type can represent all possible values of the smaller type. Assigning an int to a double does not lose information, since all int values can be represented as double values. This is known as widening conversion.
When assigning a value from a larger type to a smaller type, Java requires you to use an explicit cast. This is because the smaller type might not be able to represent all values of the larger type, which can lead to data loss or unexpected results. Casting a double to an int will truncate the decimal part, and casting an int to a byte can cause the value to wrap around if it is outside the range of a byte. This process is called narrowing conversion.
Main.java
1234567891011121314151617package com.example; public class Main { public static void main(String[] args) { int i = 150; double d = i; // Implicit widening conversion: int to double System.out.println("int to double: " + d); // 150.0 double d2 = 123.456; int i2 = (int) d2; // Explicit narrowing conversion: double to int System.out.println("double to int: " + i2); // 123 int i3 = 300; byte b = (byte) i3; // Explicit narrowing conversion: int to byte System.out.println("int to byte: " + b); // 44 (data loss due to overflow) } }
1. Which of the following primitive type conversions can be performed implicitly in Java?
2. What is the result of casting the value 9.99 (as a double) to an int in Java?
Merci pour vos commentaires !
