String#format

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);

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# 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"

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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

#Java

上次更新: 2026/10/18, 22:14:48

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