Use java's Character.isUpperCase() function to determine whether a character is an uppercase letter

Use java's Character.isUpperCase() function to determine whether a character is an uppercase letter

In Java programming, sometimes we need to determine whether a character is an uppercase letter. Fortunately, Java provides a very convenient way to achieve this function, which is to use the isUpperCase() function of the Character class. This article will introduce how to use this function to make judgments and illustrate it with code examples.

First of all, we need to understand the role of the isUpperCase() function of the Character class. The function of this function is very simple, it is to determine whether a character is an uppercase letter. Its use is very simple. You only need to pass the character to be judged as a parameter to this function and receive the return value of the function. If the return value is true, the character is an uppercase letter; otherwise, the character is not an uppercase letter.

The following is a code example that uses the isUpperCase() function to determine whether a character is an uppercase letter:

public class IsUpperCaseExample {
    public static void main(String[] args) {
        char ch1 = 'A'; // 大写字母A
        char ch2 = 'a'; // 小写字母a

        boolean isUpperCase1 = Character.isUpperCase(ch1);
        boolean isUpperCase2 = Character.isUpperCase(ch2);

        System.out.println(ch1 + " 是大写字母吗? " + isUpperCase1);
        System.out.println(ch2 + " 是大写字母吗? " + isUpperCase2);
    }
}

In this code, we define two character variables ch1 and ch2, which are initialized as Uppercase 'A' and lowercase 'a'. Then, we use the isUpperCase() function of the Character class to determine whether the two characters are uppercase letters, and assign the return value to the Boolean variables isUpperCase1 and isUpperCase2. Finally, we output the judgment results to the console through the System.out.println() function.

Execute the above code, and the output result is:

A 是大写字母吗? true
a 是大写字母吗? false

As you can see, the uppercase letter 'A' is judged to be true, that is, it is an uppercase letter; the lowercase letter 'a' is judged to be true is false, that is, it is not an uppercase letter.

It should be noted that the isUpperCase() function can only determine whether a character is an uppercase letter. For the determination of multiple characters, we need to use a loop statement to achieve it. The following is a code example that uses a loop statement to determine whether all characters in a string are uppercase letters:

public class IsAllUpperCaseExample {
    public static void main(String[] args) {
        String str = "HELLO WORLD";
        boolean isAllUpperCase = true;

        for (int i = 0; i < str.length(); i++) {
            char ch = str.charAt(i);
            if (!Character.isUpperCase(ch)) {
                isAllUpperCase = false;
                break;
            }
        }

        System.out.println(str + " 中的字符是否全部为大写字母? " + isAllUpperCase);
    }
}

In this code, we define a string variable str and initialize it to "HELLO WORLD". Then, we use a Boolean variable isAllUpperCase to indicate whether the characters in the string are all uppercase letters, which defaults to true. Then, iterate through each character in the string through a for loop. If there is a character that is not an uppercase letter, set isAllUpperCase to false, and use the break statement to jump out of the loop. Finally, we output the judgment result through the System.out.println() function.

Execute the above code, and the output result is:

HELLO WORLD 中的字符是否全部为大写字母? false

This shows that the characters in the string "HELLO WORLD" are not all uppercase letters.

To summarize, in Java programming we can use the isUpperCase() function of the Character class to determine whether a character is an uppercase letter. Depending on whether the return value is true or false, we can flexibly apply this function to perform corresponding logical operations. I hope the code examples in this article can help readers better understand and use this function.

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