為什麼在 Java 中將'1”轉換為字元會導致空輸出？

Unveiling the Mysteries of Converting Integers to Characters in Java

Converting integers to characters in Java is a common task but can be confusing if not understood correctly. This article sheds light on the intricacies involved in this conversion and provides solutions to potential issues.

The Mystery Behind the Empty Output

Consider the code snippet below:

int a = 1;
char b = (char) a;
System.out.println(b);

In this case, the output will be an empty string. The reason for this lies in the Unicode encoding scheme used by Java. When the integer a is converted to a character using the (char) cast, it is interpreted as the Unicode code point 1, which corresponds to the start-of-heading character. This character is non-printable, hence the empty output.

The '1' Trick

In contrast, the following code snippet will print the character "1":

int a = '1';
char b = (char) a;
System.out.println(b);

This is because the single quotes in the initialization of a indicate that we are dealing with a character literal. In this case, the character '1' corresponds to the Unicode code point 49, which is the character "1".

Converting Digits to Characters

If you wish to convert a digit (0-9) to a character, you can add 48 to the digit and then typecast it to a character:

int digit = 7;
char c = (char) (digit + 48);
System.out.println(c); // Output: '7'

Alternatively, you can use the Character.forDigit() method:

int digit = 7;
char c = Character.forDigit(digit, 10);
System.out.println(c); // Output: '7'

Converting Unicode Code Points to Characters

To convert an integer that represents a Unicode code point to a character, you can use the Character.toChars() method:

int codePoint = 65;
char[] chars = Character.toChars(codePoint);
char c = chars[0];
System.out.println(c); // Output: 'A'

By understanding these techniques, you can confidently convert integers to characters in Java, avoiding any confusion or unexpected outputs.

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