Métodos Básicos em String - Parte 2

Putting Methods into Practice

Now, let's dive into code examples for each of these methods. You'll quickly grasp their functionality:

Main


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package com.example;

public class Main {
    public static void main(String[] args) {
        String string = "Hello world";
        System.out.println("string length = " + string.length());
        System.out.println("char at 0s position is " + string.charAt(0));
        System.out.println("substring from third position = " + string.substring(3));
        System.out.println("substring from third to seventh position = " + string.substring(3, 7));
        System.out.println("string in lower case = " + string.toLowerCase());
        System.out.println("string in upper case = " + string.toUpperCase());
        System.out.println("checking if string contains 'ell' = " + string.contains("ell"));
        System.out.println("replacing all the 'l' characters to 'b' = " + string.replace('l', 'b'));
        char[] chars = string.toCharArray();

        System.out.println("as we can see, after all of this " +
                "operations our string hasn't changed, it is still " + string);
    }
}

We just used many methods on a single string, but in the end, its value remained unchanged. That's exactly what I mentioned in the previous section. The value of a string doesn't alter without creating a new object in memory.

Now, let's explore a few practical applications of these methods through the following example tasks:

Acabamos de usar vários métodos em uma única string, mas, no final, seu valor permaneceu inalterado. Isso é exatamente o que mencionei na seção anterior. O valor de uma string não se altera sem a criação de um novo objeto na memória.

Agora, vamos explorar algumas aplicações práticas desses métodos através das seguintes tarefas de exemplo:

Main


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package com.example;

public class Main {
    public static void main(String[] args) {
        String string = "Make Java great again";
        char[] array = string.toUpperCase().toCharArray();
        //as you can see we can use multiple methods in one line
        for (char element : array) {
            System.out.print(element);
        }
        //we use for-each loop to print every element of our array
    }
}

Task 2

Given a string that contains the word "helicopter," your task is to remove all the unnecessary letters from this string and display the new string on the screen, replacing all occurrences of the letter "e" with "u."

Task 2

You upload a document title, and it needs to be converted to uppercase with underscores _ added between words to create a system-friendly filename.

Main


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package com.example;

public class Main {
    public static void main(String[] args) {
        String documentTitle = "Quarterly financial report"; // Document title
        String systemFileName = documentTitle.toUpperCase().replace(" ", "_");
        
        System.out.println(systemFileName); // Output
    }
}

This code processes a document title to create a system-friendly filename. It uses toUpperCase() to convert all letters to uppercase and replace(" ", "_") to replace spaces with underscores, ensuring consistency and compatibility for file storage. The result is then displayed on the console.

1. O que será impresso no console?

2. Qual será a mensagem impressa no console?

3. What will be printed to the console?

Tudo estava claro?

Obrigado pelo seu feedback!

Seção 5. Capítulo 3