What does colon mean in java

The colon (:) in Java is mainly used to declare variable types, type conversions, specify condition ranges, specify for loop step sizes, indicate case branches, jump out of nested loops, and indicate comments.

Colon in Java

The colon (:) in Java is mainly used for the following purposes:

1. Declare variable type:

int age; // 声明一个 int 类型的变量 age

2. Type conversion:

int num = (int) 3.14; // 将 double 类型的值 3.14 转换为 int 类型

3. Express in conditional statement Range:

if (age >= 18 && age < 65) {
    // 年龄在 18 岁到 65 岁之间
}

4. Specify the step size in the for loop:

for (int i = 0; i < 10; i += 2) {
    // 循环 i，步长为 2
}

5. Express the case branch in the switch statement:

switch (option) {
    case 1:
        // case 1 分支
        break;
    case 2:
        // case 2 分支
        break;
    default:
        // 默认分支
}

6. Jump out of the nested loop in the jump out label statement:

outer:
for (int i = 0; i < 10; i++) {
    inner:
    for (int j = 0; j < 10; j++) {
        if (j == 5) {
            break outer; // 跳出 outer 循环
        }
    }
}

7. Indicate comments:

// 这是单行注释
/* 这是多行注释 */

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