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- java mutable classes and immutable classes
- A Java mutable class means that after obtaining an instance of this class, the content of the instance can be changed, such as changing the internal member variables of this instance; an immutable class means that after obtaining an instance of this class, the contents of the instance cannot be changed. Once an immutable instance Once created, the values of its internal member variables cannot be changed.
- JavaBase 2061 2019-11-14 09:54:35
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- Solve the problem that the browser does not support java
- Solution to the problem that the browser does not support Java: 1. Click on the browser settings option; 2. Click on the Internet options; 3. Click on the security option; 4. Click on the custom level; 5. Find "java applet script" and click "Enable" That’s it.
- JavaBase 21811 2019-11-14 09:40:53
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- Java determines whether a variable is empty
- How to determine whether a variable is empty in java: first import the org.springframework.util package; then use "StringUtils.isEmpty(Object str);" to determine; finally, you can determine that the variable is empty based on the returned value being false.
- JavaBase 4416 2019-11-14 09:32:55
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- Java determines whether an array contains a certain value
- How to determine whether an array contains a certain value in Java: 1. Create a findStr function and pass in two parameters: the array and the value to be found; 2. Use a for loop within the function to traverse the array; 3. Use equals to determine whether the array element is There are elements that are the same as the value to be found; 4. If there are the same elements, the array contains this value.
- JavaBase 6234 2019-11-14 09:20:17
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- What are the basic interfaces of Java collection class framework?
- The basic interfaces of the Java collection class framework have two major interfaces: Collection and Map, one is a collection of elements and the other is a collection of key-value pairs; among them, the List and Set interfaces inherit the Collection interface; HashMap and HashTable implement the Map interface.
- JavaBase 4055 2019-11-14 09:08:21
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- what is java expression
- A Java expression is a combination of variables or constants and symbols, ending with a semicolon ";". The main categories of Java expressions include arithmetic expressions, assignment expressions, conditional expressions and logical expressions.
- JavaBase 3826 2019-11-13 17:37:00
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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.
- JavaBase 2451 2019-11-13 17:39:48
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- 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.
- JavaBase 3141 2019-11-13 17:22:47
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- 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.
- JavaBase 3670 2019-11-13 17:16:44
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- 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.
- JavaBase 6877 2019-11-13 17:08:08
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- 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.
- JavaBase 3831 2019-11-13 17:01:25
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- 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.
- JavaBase 5449 2019-11-13 16:37:57
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- 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.
- JavaBase 5399 2019-11-13 16:29:25
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- 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.
- JavaBase 10146 2019-11-13 16:12:04
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- 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.
- JavaBase 3004 2019-11-13 15:53:08
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