Java String
Parsa Hejabi
Table of Contents
- What is a String?
- How it is implemented in Java?
- What are predefined methods for Strings in Java?
"Hello, World...!"
What is a String?
- A sequence of characters.
- In Java, Strings are treated as objects.
- String is a predefined Class in Java.
- Like any class that you create...
String Class
- You can create a string by just typing OR create with "new" keyword...
- 11 constructors for String class.
String greeting = "Hello world!";public class StringDemo {
public static void main(String args[]) {
char[] helloArray = { 'h', 'e', 'l', 'l', 'o', '.' };
String helloString = new String(helloArray);
System.out.println(helloString);
}
}
//hello.!
The String class is immutable so that once it is created a String object cannot be changed.
What is Immutable?
- Immutable means unmodifiable or unchangeable.
- Once string object is created, its data or state can't be changed but a new string object is created.
public class testImmutableString {
public static void main(String args[]) {
String s = "salam ";
s.concat("Java");
//concat() method appends the string at the end
System.out.println(s);
}
}
//will print Sachin because strings are immutable objects.Immutable
Format Strings
- Methods: .printf(), .format()
System.out.printf("The value of the float variable is " +
"%f, while the value of the integer " +
"variable is %d, and the string " +
"is %s", floatVar, intVar, stringVar);String fs;
fs = String.format("The value of the float variable is " +
"%f, while the value of the integer " +
"variable is %d, and the string " +
"is %s", floatVar, intVar, stringVar);
System.out.println(fs);Characters in Java
- Unicode
- Problems in ASCII.
- The Unicode standard is a character set.
- Characters are saved as numbers.
- What is encoding?
- UTF-8, UTF-16, UTF-32
- The default for Java is UTF-16.
Escape characters
- New line: "\n"
- Tab: "\t"
- ": "\""
- ': "\'"
- \: "\\"
String S = "Salam\\ Ok\' Bye\"";
System.out.println(s);
//Salam\ Ok ' Bye"