I don’t know if you know the simple data types of Java. The following are five simple data types representing numbers and characters, and provide detailed explanations and analysis.
1. Simple data type initialization
In Java language, simple data types are automatically initialized to default values when declared as member variables of a class, unless explicitly declared. Simple data type is not automatically initialized when a method declares a local variable and causes the compiler to throw an error message similar to the following "Variable x may not have been initialized.(x variable is not initialized)" Table B defines the default value of Java simple data type.
2. Packaging
1ava also provides built-in encapsulation classes such as Byte, Short, Boolean, Character, Integer, Double, Float and Long. These wrapper classes provide intuitive and practical methods. For example, Byte, Float, Integer, Long, and Double classes all have doubleValue() methods, through which values stored in instances of the class can be converted to Double type. Also, all encapsulation classes provide a static valueOf(String s) method to put the given String.
3. Data type
Data types are abstract expressions of memory locations. Programmers can take advantage of a variety of data types: some are defined by programming languages, some are defined by external libraries, and some are defined by programmers. Many programming languages rely on specific computer types and specific compilation implementations of data type attributes, such as the size of word and integer data types. On the other hand, Java's virtual machines are responsible for defining all aspects of their built-in data types. This means that no matter how low-level operating system the Java virtual machine (JVM) runs on, the properties of the data type are exactly the same.
4. The default initial value of Java simple data type
The code in Listing B shows that all Java simple data types are used as member variables of the Initialization class. This example also shows that an int variable is locally declared in the constructor of the Initialization class. Without modifying the above code, the compiler will throw an error when compiling the above code.
Once the lines of code that caused the problem (those that reference uninitialized variables caused the error) were deleted or commented out.
Summary: Java defines a complete set of simple data types. In addition, Java cancels the hardware and compiler dependencies that have become languages, allowing programmers to turn their attention to other issues. In the next article, we will continue to discuss some of the frequently used, Java-defined complex data types, and learn how to use them to deal with typical programming problems.
5. Simple data types of Java
All numeric variables in Java are signed, and Java does not allow arbitrary conversions between data types. Only type conversions can be performed between numeric variables. For example, boolean cannot be converted to other data types, and other data types cannot be converted to boolean. Because Java's simple data types are accurately defined, and direct memory access is not allowed, the sizeof operator is cancelled in the Java language. Java's simple data types are not objects. In order to treat Java simple data types in an object-oriented way, you need to encapsulate them first with classes.
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