Common String Practices

Strings are objects that represents a combination of characters.

Joining Two Strings

Two strings can be joined by using the concatenation operator or method.

// Using the operator
String first = "Mr. ";
String last = "Park";

String full_name = first + last;
System.out.println(full_name); // Outputs: Mr. Park

// Using the method
String a = "Hello";
String b = a.concat(" World!");

System.out.println(b); // Outputs: Hello World!

Get Individual Characters from a String

String objects are composed of individual character primitive values; therefore, we can obtain individual characters from a string by using charAt(index). Indexing starts at 0 for Strings.

String fruit = "Strawberry";
char target = fruit.charAt(2);
System.out.println(target); // Outputs r

Determine the number of characters in a String

.length() method is used to obtain the size of a string.

String fruit = "Strawberry";
int size = fruit.length();
System.out.println(size); // Outputs 10

Check a String's prefix or suffix

We can determine if a string starts with a certain pattern or if it ends with a certain pattern.

String a = "Hello";
boolean start = a.startsWith("He");
boolean end = a.endsWith("lo!");

System.out.println(start + " " + end); // Outputs true false

Replace a certain pattern in a String

We can search for a pattern within a String and replace all occurrence of it.

String a = "Hello";
a = a.replace("ello", "i");
        
String b = "W O R L D";
b = b.replace(" ", "");
        
System.out.println(a + " " + b); // Outputs Hi WORLD

Using a Loop on a String

Since Strings are indexable, we can utilize both a while loop and for loop to traverse individual characters one-by-one.

// While Loop Method
String word = "Hello!";
int i = 0;

while (i < word.length()) {
    System.out.println(word + " at Index I is: " + word.charAt(i));

    i++;
}

/* Outputs:
Hello! at Index I is: H
Hello! at Index I is: e
Hello! at Index I is: l
Hello! at Index I is: l
Hello! at Index I is: o
Hello! at Index I is: !
*/

// For Loop Method
String word = "Hello!";

for (int i = 0; i < word.length(); i++) {
    System.out.println(word + " at Index I is: " + word.charAt(i));
}

/* Outputs:
Hello! at Index I is: H
Hello! at Index I is: e
Hello! at Index I is: l
Hello! at Index I is: l
Hello! at Index I is: o
Hello! at Index I is: !
*/