Impara Formatting Numbers and Alignment | Mastering String.format()

Mastering number formatting and alignment in Java is essential for producing clear and professional console output. The String.format() method gives you precise control over how numbers and text are displayed. By specifying width, precision, and alignment options, you can ensure that your output is both readable and visually appealing. Understanding these formatting tools is particularly important when you need to present data in columns, such as in tables or reports.

Main.java


              123456789101112131415
            
package com.example;

public class Main {
    public static void main(String[] args) {
        double price1 = 5.2;
        double price2 = 15.75;
        double price3 = 123.456;

        System.out.println(String.format("%-10s %10s", "Item", "Price"));
        System.out.println(String.format("%-10s %10.2f", "Apple", price1));
        System.out.println(String.format("%-10s %10.2f", "Banana", price2));
        System.out.println(String.format("%-10s %10.2f", "Cherry", price3));
    }
}

In the example above, you see how width and precision specifiers work together to control the appearance of your output. The width specifier (such as 10 in %10.2f) reserves a minimum number of characters for the value, ensuring that columns align neatly. The precision specifier (.2 in %10.2f) controls the number of digits displayed after the decimal point for floating-point numbers. By combining these specifiers, you can format numbers to a desired precision and align them within columns, making your output much easier to read and compare.

Main.java


              123456789101112131415
            
package com.example;

public class Main {
    public static void main(String[] args) {
        String name1 = "Alice";
        String name2 = "Bob";
        int score1 = 95;
        int score2 = 87;

        System.out.println(String.format("%-10s | %5s", "Name", "Score"));
        System.out.println(String.format("%-10s | %5d", name1, score1));
        System.out.println(String.format("%-10s | %5d", name2, score2));
    }
}

1. Which flag in String.format() is used for left alignment of text?

2. Fill in the blank: To format a double to 3 decimal places, use the format specifier ______.

3. How does specifying a width in String.format() affect the output?

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Grazie per i tuoi commenti!

Sezione 1. Capitolo 2

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Suggested prompts:

Can you show me a code example using String.format() with width and precision?

How do I align text to the left or right using String.format()?

What other formatting options are available in Java for console output?

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Main.java


              123456789101112131415
            
package com.example;

public class Main {
    public static void main(String[] args) {
        double price1 = 5.2;
        double price2 = 15.75;
        double price3 = 123.456;

        System.out.println(String.format("%-10s %10s", "Item", "Price"));
        System.out.println(String.format("%-10s %10.2f", "Apple", price1));
        System.out.println(String.format("%-10s %10.2f", "Banana", price2));
        System.out.println(String.format("%-10s %10.2f", "Cherry", price3));
    }
}

Main.java


              123456789101112131415
            
package com.example;

public class Main {
    public static void main(String[] args) {
        String name1 = "Alice";
        String name2 = "Bob";
        int score1 = 95;
        int score2 = 87;

        System.out.println(String.format("%-10s | %5s", "Name", "Score"));
        System.out.println(String.format("%-10s | %5d", name1, score1));
        System.out.println(String.format("%-10s | %5d", name2, score2));
    }
}

1. Which flag in String.format() is used for left alignment of text?

2. Fill in the blank: To format a double to 3 decimal places, use the format specifier ______.

3. How does specifying a width in String.format() affect the output?

Tutto è chiaro?

Grazie per i tuoi commenti!

Sezione 1. Capitolo 2