Java

In the Java interview HashMap should say a required topic, and HASHMAP and HashSet are two important members of the Java Collection Framework, where HashMap is the common implementation class of the Map interface, HashSet is Set Common

First, the Static class1. Definition of static classStatic, which can be used to modify the properties or methods of a class, is known as statics.If a property of a class, regardless of how many objects are created, has only one storage space for

One, array1. The concept and function of arraysAn array is a collection of elements of the same data type;The array itself is a reference data type, that is, an object. But arrays can store basic data types, or they can store reference data

Java memory Model and the JVM Memory ManagementOne, theJava memory model:1. main memory and working memory (that is, local memory):　　The main goal of the Java memory model is to define access rules for variables in the program, that is, the

One.Here begins the application of the IF statement and expands the operation experiment.In the case of judging the input data for the day of the week, it proves that I have not understood the = = comparison operator well enough to understand the if

The difference between keywords continue, break, and return in Java:Continue: Jump out of this loop to continue the next cycleBreak: Jumps out of the loop body and resumes execution of the function body outside the loopReturn: Jumps out of the

PackageCom.imooc.text;/*** Third-order Magic side 8 Results *@authorsouth of the north of Mexico **/ Public classMagic { Public Static voidMain (string[] args) {intA = 0, B = 1; Square1 (A, b); System.out.println (); Square2 (A,

Type parameters cannot be instantiated with a base type You cannot replace a base type with a type parameter: for example, there is no pair, only pair The reason is the type erase. After erasing, the pair class contains a field of type Object ,

I've never figured out the difference between a string and a null string, and today the code has been nullpointerexception, and I haven't figured it out.String s = null;s = xxx.getstring ();if (!s.isempty () && s! = null) {System.out.println ("OK");}

Will all areas in the JVM's memory be recycled?First we know that the Java stack and the local method stack after the completion of the method execution of the corresponding stack frame immediately out of the stack destroyed, the recovery of the two

Xmind use of Java for development, if there is a memory overflow problem, then must be a desktop shortcut problem, the solution is to directly modify the contents of the shortcut, modified as follows:[Desktop

SQL Injection: add 'or '1' = '1' to the MySQL database Authentication secret in java. Add 'or '1' =' 1 to the password string to create a universal password. The reason is as follows: In the original code, the password is 123456. Execute

JVM garbage collection algorithm and jvm garbage collection 1. Mark-cleanup algorithm: the most basic garbage collection algorithm. Just like its name, the algorithm consists of two steps: Marking and cleanup: first, marking the objects to be

Java uses POI to generate an excel table with a linked drop-down box. JA learning record for an ava primary school student. Import java. io. file; import java. io. fileNotFoundException; import java. io. fileOutputStream; import java. io.

Java I/O input/output stream details, java detailsIntroduction Java IO streams are essential to read and write files in Java. This blog post mainly introduces the content of the input and output streams in Java, including File encoding, File class

Full Java basics and full Java Basics This is a full set of basic java knowledge that I have prepared in my previous lectures. It can also be used by beginners for intermediate programmers. I have made it a chm document type. You can download the

Article 1-Understanding Jmeter and Article 1-jmeter Jmeter is a Java-based stress testing tool developed by Apache. It was initially designed for Web application testing, but later expanded to other testing fields. It can be used to test static and

Spring transaction exception rollback, capture exceptions do not throw will not roll back, spring transaction I recently encountered a situation where transactions do not roll back. I also want to say that there is a bug in JPA transactions? I think

Principles, configuration, and usage of Tomcat data sources1. The role and operating principle of the data source can be improved by using the data source in the program code. The performance improvement depends on the operating

Data inconsistency between the two ends of the object stream: data inconsistency between the two ends of the streamData inconsistency between the two ends of the object stream:Status when sending and receiving data for the server: There are two