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Principle of automatic loading in PHP and tutorial on using __autoload

The principle of automatic loading in PHP: When adding a new class, if the PHP system cannot find the class, it will automatically call the __autoload($class_name) method in this file, and the new class_name becomes the parameter of this method.

Nov 13, 2019 pm 05:32 PM

php principle Tutorial autoload

Java prompts that the system cannot find the specified file

Solution to the java prompt that the system cannot find the specified file: 1. Check whether the file path is correct; 2. When creating a file, first use mkdirs to create the parent directory, and then use createNewFile to create the file.

Nov 13, 2019 pm 05:22 PM

java

Several common locks in Java

Common locks in Java are: 1. Spin lock; 2. Heavyweight lock; 3. Bias lock; 4. Lightweight lock; 5. Fair and unfair lock; 6. Pessimistic lock; 7. Optimistic lock.

Nov 13, 2019 pm 05:16 PM

java Lock

How many bytes does char occupy in Java?

In Java, char occupies 2 bytes. Java uses Unicode encoding, and 2 bytes represent one character. When numbers are stored in English, the first byte is 0, and when Chinese characters are stored, they occupy two bytes.

Nov 13, 2019 pm 05:08 PM

char java

How to understand enumeration types in Java

In Java, when a variable has multiple fixed values, it can be defined as an enumeration type. You must use the enum keyword when declaring an enumeration, and then define the name, accessibility, base type, members, etc. of the enumeration.

Nov 13, 2019 pm 05:01 PM

java enumeration type understand

How to install java

How to install java: 1. Go to the java official website and download the jdk installation package; 2. Double-click the installation package to install according to the guidance; 3. Right-click My Computer - Advanced System Settings - Environment Variables and add the JAVA_HOME variable to the jdk directory; 4. Finally, in Path Just add the bin directory after the variable.

Nov 13, 2019 pm 04:37 PM

java Install

Several uses of this keyword in java

The uses of this keyword in Java are: 1. Call methods of this class; 2. Call attributes of this class; 3. Call other constructors of this class; 4. Call methods of the same name of the parent class or other specified classes.

Nov 13, 2019 pm 04:29 PM

java this Keywords usage

Java can't find the main method?

The solution to the problem that java cannot find the main method: first check the format of the main function; then open eclipse-window-preference-run and debug-Lunching; and finally change the first line of configuration to always.

Nov 13, 2019 pm 04:12 PM

java main not found

What are java value types

Java value types are basic data types, including four data types: integer, floating point, character, and logical. Value type data is stored in the stack, has faster access speed, and has a short life cycle.

Nov 13, 2019 pm 03:53 PM

java value type

What are the types of errors in java?

Error types in Java can be abstractly divided into three categories, which are: 1. Syntax errors, which are caused by input that does not conform to the grammatical rules during programming; 2. Run errors, which occur during the running of the program; 3. Logic errors, which occur when the program is running. Get the expected results.

Nov 13, 2019 pm 03:45 PM

java Error type

or how to express it in java

The representation method of or in Java is "||", two vertical lines, above the enter key on the keyboard. "||" is a logical operator in Java. It is followed by Java expressions. When any expression is true, the result is true.

Nov 13, 2019 pm 03:33 PM

java Logical Operators

How to write java in jsp

How to write java in jsp: 1. Use "<%!declaration statement%>" for declaration statements, usually global variables, constants, methods; 2. Use "<%java code%>" for writing local variables and java statements; 3. Use "<%=java code%>" for jsp expression, please note that it cannot be followed by a semicolon.

Nov 13, 2019 pm 03:14 PM

java jsp

What are the common exceptions in java

Several common exceptions in Java are: 1. NullPointerException; 2. ClassCastException type cast exception; 3. ArrayIndexOutOfBoundsException array subscript exception.

Nov 13, 2019 pm 03:11 PM

java common abnormal

Several common exceptions in java

Several common exceptions in Java are: 1. NullPointerException; 2. ClassCastException type cast exception; 3. ArrayIndexOutOfBoundsException array subscript exception.

Nov 13, 2019 pm 03:10 PM

java common abnormal