Created: 2023-08-26 16:05
Status: #concept
Subject: Programming
Tags: Java Java Data Type java.util.Scanner java.lang.StringBuilder

Java String Class

Scanner scan = new Scanner(System.in);

// getting user input
String userInput = scan.nextLine();

// string concatenation & string interpolation
System.out.println("You inputted: " + userInput); 
System.out.println(String.format("You inputted: %s", userInput));

// typecasting to string
Integer someInteger = 777;
System.out.println(String.valueOf(someInteger));
System.out.println(someInteger.toString());
System.out.println("" + someInteger);

static Methods

• String.format(fmt, ...args) acts like stdio.h's printf function which converts a Format String's Conversion Specifiers based on the ...args and returns it.
  • to pad integers, we need to use %0Pd, where P is the maximum number of padding to occupy like %.Pd in printf see here.
• String.valueOf(anyTypeValue) converts anyTypeValue into a String.

Instance Methods

• .length() returns the number of characters in the string.
  • .isEmpty() returns true if .length() is 0.
• .equals(String aString) checks if the instance is equal to aString.
• .startsWith(String aString): boolean same as JavaScript.
• .repeat(int num) concatenates the string instance by itself num times.
• .split(Pattern delimiter) returns a String[] containing the strings in between each delimiter, similar to JavaScript.
  • if delimiter.equals(""), it will split each letter into individual strings.
• .join(String delimiter, Iterable<String> iterable) joins an iterable string or java.lang.StringBuilder CharSequence.
• .trim(): String removes any leading & trailing whitespaces.
• .contains(String substr) returns true if the instance contains a substr, otherwise false.
• .charAt(int index) returns a String of the character at the index.
• .compareTo(String s) returns an int for java.util.Comparable interfaces.
  • .compareToIgnoreCase(String s) does the same, but ignores capitalization.

References

• Oracle Documentation