String concatenation is a common operation in Java programming. It is to concatenate multiple strings into a single string. Java provides a String class which is an immutable class which means the object cannot be mutated once instantiated.Once a String object is instantiated, its properties cannot be changed anymore, so when concatenating strings, it's actually create a new String instance to store the concatenated string values. For example, below is a simple string concatenation example.String s = "abcd";s = s.concat("ef");When this piece of code is executed, a new String instance is create...

In Java, == is used to compare whether two objects have the same memory location, equals() is usually used to compare whether two objects have the same time and the same state.  When comparing two strings, normally we just want to know whether they have same content, so we can choose equals(). But since String comparison is so frequently needed, Java has worked on the String class to make == workable when comparing two String literals.The String class maintains a pool of empty string literals initially. Then when a new string is created, this new string will checked against...

String is immutable in Java. This means once a String object is created and instantiated, that object cannot be changed. Any operation on the String object will create a new Object instead of operating on the original content. Below are three images to help you understand String immutability in Java.Declare a StringString s = "abcd";s stores the reference to the string content created in the heap.Assign the String reference to another String variableString s2 = s;s2 stores the same reference to the same String object. Since the content is not changed, there will be only one actual object ...

In Java, String.length() is to return the number of characters in the string, while String.getBytes().length is to return the number of bytes to represent the string with the specified encoding. By default, the encoding will be the value of system property file.encoding, the encoding name can be set manually as well by calling System.setProperty("file.encoding", "XXX"). For example, UTF-8, Cp1252. In many cases, String.length() will return the same value as String.getBytes().length, but in some cases it's not the same.String.length() is the number of UTF-16 code units needed to represent the s...

Prior to C++11, there is no built-in function in C++ standard library which can be used to convert numbers such as interger and double number to string.  There are many ways which can convert number to string. Since C++ is C compatible, we can use itoa() function to convert an integer to C style string. But this one can only convert integer to string, not double. For different types of numbers, we need to use different functions.string s = string(itoa(a));Actually, we can also use stringstream in C++ to convert number to string.  Also, here since we want to convert different types of...