more: link (opens new window)

• %d: long, int
• %s: String, boolean, object
• %f: float
  • %.1f: Formats a floating-point number with 1 decimal places. 这里不能加 0, 如 0.xxx
  • %.2f: Formats a floating-point number with 2 decimal places

包装类型

需要判空

Integer count = null;
System.out.printf("Count: %d%n", count != null ? count : 0);

通用方式

Integer count = null;
Double ratio = 2.345;
System.out.printf("Count: %s, Ratio: %s%n", String.valueOf(count), String.valueOf(ratio));
// Output: "Count: null, Ratio: 2.345"

优点: 这处理方式既能避免空指针异常,还保持了输出的通用性,非常适合于不确定类型或可能为 null 的变量