Contents

Strings in Java

Let’s look at some basic String operations in Java.

String s = "Almost winter break";

s.substring(0,3)

Alm

s.substring(4,7)

st 

s.toUpperCase()

ALMOST WINTER BREAK

s.toLowerCase()

almost winter break

String[] array = s.split(" ")

System.out.println(array)

[Ljava.lang.String;@5e19b040

System.out.println(Arrays.toString(array))

[Almost, winter, break]

for (String s : array) { 
    System.out.println(s); 
}

Almost

winter

break

ArrayLists

ArrayLists are the functional equivalent of Lists in Python. See some sample usage cases below.

ArrayList<String> alist=new ArrayList<String>();  
alist.add("Jeannie");
alist.add("Rohit");
alist.add("Lida");
alist.add("Steve");
alist.add("Dan");
alist.add("Sam");

true

System.out.println(alist)  // print the list 

[Jeannie, Rohit, Lida, Steve, Dan, Sam]

alist.add(3, "Iris") // add Iris to index 3

System.out.println(alist)

[Jeannie, Rohit, Lida, Iris, Steve, Dan, Sam]

alist.get(2) // get the element at index 2

Lida

// set index 5 to Steve (returns old value)
alist.set(5, "Steve")  

Dan

System.out.println(alist)

[Jeannie, Rohit, Lida, Iris, Steve, Steve, Sam]

Arrays

import java.util.Arrays;

String [] myList = new String[6];

String [] myList = {"Jeannie", "Rohit", "Lida", "Steve", "Dan", "Sam"};

System.out.println(Arrays.toString(myList));

[Jeannie, Rohit, Lida, Steve, Dan, Sam]

System.out.println(myList[2])

Lida

myList[4] = "Aaron"

Aaron

System.out.println(Arrays.toString(myList))

[Jeannie, Rohit, Lida, Steve, Aaron, Sam]

// create an array of 3 integer elements, all initialized to 0
int [] myList = new int[3]

System.out.println(Arrays.toString(myList))

[0, 0, 0]

// create an array of 3 String elements, all initialized to null
String [] myList = new String[6];
System.out.println(Arrays.toString(myList))

[null, null, null, null, null, null]