String b = "abcd"
String a = "a"
String c = "bcd"
String d=a+c
system.out.println (dashed constants) / / false
Why false should be true according to the principle that there is only one copy of the java string constant.
what does the memory diagram look like here
String needs to use the equals method when comparing values. B.equals (d) returns the reference address of the string "abcd" as the object of true,b, while d is a new object after the splicing of "a" and "bcd". The reference addresses of the two are different, so = = what is returned is the magic of the false, memory diagram, and I am also a good programmer.
JAVA
when can this kind of virtual machine optimization be regarded as a principle? Oh, my God, who gave you that guarantee?
String d = a + c;
assignment is, of course, . is calculated when this sentence is executed. It calculates a new variable, not the one in the string constant pool.
speaking, there is also an optimization problem. string concatenation is optimized to be similar to the StringBuilder operation .
if you have to say, why constant calculations can be calculated when they are not compiled directly , then we are done.
this is a question of program correctness , not a matter of optimization.
first of all, it is clear that the reference data type = = compares the address value, and APCC is the StringBuffer in action
dabilb is false because it actually creates a StringBuffer object, and then uses the StringBuffer object to execute the append method to create the string object "abcd", call toString, and then convert it to String. But the converted String object, which creates the object, is put in the heap to point to the reference to the memory address, while c is a string constant, so of course it is not equal, ah, the key point is to get the string string by adding string.
Previous: How to identify the built-in less file in vscode?
Next: How can the data in the mongoose query table be saved?
Student.java private int age; private String name; public Student(int age, String name){ this.name = name; this.age = age; } public void setAge(int age) { this.age = age; } public String getName() { return name; } public void setNam...
but what if I call system.in.read () again after closing it? does its instance BufferedInputStream shut down automatically immediately after it is used up? Or are you waiting for recycling? ...
the first code can be locked successfully public class Main { public static void main(String[] args){ LockThread lock1 = new LockThread(true); LockThread lock2 = new LockThread(false); Thread thread1 = new Thread(lock1); Thread th...
< H2 > NewFile.java < H2 > private File configurationFile; public NewFile(File file){ this.configurationFile = file; } public void newFile() throws IOException{ if (!configurationFile.exists()) configurationFile.createNewFile(); ...
objects are transmitted in binary mode on the network. so for serialization, different serialization, the transferred object should be a binary stream. then why json and xml are also described as serialization. It is not very clear that both of them ha...
java rookie, read java Core Technology introduction Graphics2D class is a subclass of Graphics, in which there is a code public void paintComponent (Graphics g) { Graphics2D g2 = (Graphics2D) g ...... } will there be no error in the downward transitio...
the java interface should not be instantiated, so why make the program work properly in the following form? (the screenshot on the ebook, the program actually clicked, but I don t know why) ...
URL is not hierarchical ...