Java Strings - using Strings in practice

Short overview of how String objects can be used in Java

1. Java Strings Using Strings in practice

2. Java String Character sequence Immutable Class defined in the java.lang package Instantiate a String Object: Using a String literal ( series of characters enclosed in double quotes ) String s1 = “ Cat ”; Via the String constructor ( see API for different constructors ) String s2 = new String (“ Cat ”);

3. Java String – Memory Output of the following code?

4. Java String – Memory Output of the following code? s1 == s2 : true s1 == s3 : false

5. Java String – Memory Java Memory Heap as a Java Object String s2 = new String (“ Cat ”); String pool in the Java Memory Heap String interning Flyweight pattern String s1 = “ Cat ”;

6. Java String – API Extends java.lang.Object E.g.: equals (other: Object) : boolean , hashCode () : int , … Implements: Serializable, CharSequence , Comparable<String> E.g.: compareTo (other: String) : int , charAt (index: int ) : char, … String specific API E.g.: isEmpty () : boolean , …

7. StringBuilder Mutable

8. StringBuffer Mutable Thread-safe Slower

9. Java String – Formatting String.format Conversion specifiers : %d ( decimal integer), %f ( floating point), %c ( any character ), … Many more options ( see documentation ) String fs; fs = String.format (" Variable 1 (%f) is of type float, while " + " the 2nd variable (%d) is an integer, " + " and the 3rd one, %s, is a string... ", floatVar , intVar , stringVar ); Formatter class ( java.util ) StringBuilder sbuf = new StringBuilder (); Formatter fmt = new Formatter ( sbuf ); fmt. format (" PI = % f%n ", Math .PI ); System .out. print ( sbuf. toString ()); // you can continue to append data to sbuf here.

10. Use cases String instantiation String concatenation String duplication String manipulation … => Questions : Performance? Thread-safe? …

11. Use cases – Instantiation Benchmarking: String Object: new ( with various constructors ), literal StringBuffer constructor (s) StringBuilder constructor (s)

12. Use cases – Concatenation Benchmarking: String Object: Operator +, concat method StringBuffer append StringBuilder append …

13. Conclusion Creating Java String objects Concatenating strings

14. Discussion / Questions ?

15. References Java String https://docs.oracle.com/javase/tutorial/java/data/strings.html Java String – Memory: https://www.journaldev.com/797/what-is-java-string-pool https://en.wikipedia.org/wiki/String_interning https://en.wikipedia.org/wiki/Flyweight_pattern https://www.javatpoint.com/how-to-optimize-java-string-creation Java String – API https://docs.oracle.com/javase/8/docs/api/java/lang/String.html

16. References Java String - Formatting https://docs.oracle.com/javase/7/docs/api/java/util/Formatter.html https://dzone.com/articles/java-string-format-examples StringBuilder StringBuffer