Java Math 类完全指南：abs、round、ceil、floor、min、max 等核心方法与实战示例

Java Math 类是开发者解决复杂计算的利器——从物理模拟到地理计算。本指南覆盖核心方法 abs()、round()、ceil()、floor()、min()、max() 并附实战代码示例。

java.lang.Math 关键常量：

• Math.E —— 2.718281828459045（自然对数底）
• Math.PI —— 3.141592653589793（圆周率）

下面简洁代码片段演示这些方法（无需显式导入；java.lang.Math 自动可用）：

int i1 = 27; int i2 = -45; double d1 = 84.6; double d2 = 0.45; // abs() System.out.println("abs(i1) = " + Math.abs(i1)); System.out.println("abs(i2) = " + Math.abs(i2)); System.out.println("abs(d1) = " + Math.abs(d1)); System.out.println("abs(d2) = " + Math.abs(d2)); // round() System.out.println("round(d1) = " + Math.round(d1)); System.out.println("round(d2) = " + Math.round(d2)); // ceil() & floor() System.out.println("ceil(d1) = " + Math.ceil(d1)); System.out.println("floor(d1) = " + Math.floor(d1)); System.out.println("ceil(d2) = " + Math.ceil(d2)); System.out.println("floor(d2) = " + Math.floor(d2)); // min() & max() System.out.println("min(i1, i2) = " + Math.min(i1, i2)); System.out.println("max(i1, i2) = " + Math.max(i1, i2)); System.out.println("min(d1, d2) = " + Math.min(d1, d2)); System.out.println("max(d1, d2) = " + Math.max(d1, d2));

示例输出：

abs(i1) = 27 abs(i2) = 45 abs(d1) = 84.6 abs(d2) = 0.45 round(d1) = 85 round(d2) = 0 ceil(d1) = 85.0 floor(d1) = 84.0 ceil(d2) = 1.0 floor(d2) = 0.0 min(i1, i2) = -45 max(i1, i2) = 27 min(d1, d2) = 0.45 max(d1, d2) = 84.6

除基本算术，java.lang.Math 还提供强大科学函数：

double d1 = 84.6; double d2 = 0.45; System.out.println("exp(d2) = " + Math.exp(d2)); System.out.println("log(d2) = " + Math.log(d2)); System.out.println("pow(5, 3) = " + Math.pow(5.0, 3.0)); System.out.println("sqrt(16) = " + Math.sqrt(16));

输出：

exp(d2) = 1.568312185490169 log(d2) = -0.7985076962177716 pow(5, 3) = 125.0 sqrt(16) = 4.0

三角函数工具箱：

double angleDeg = 30.0; double angleRad = Math.toRadians(angleDeg); System.out.println("sin(30°) = " + Math.sin(angleRad)); System.out.println("cos(30°) = " + Math.cos(angleRad)); System.out.println("tan(30°) = " + Math.tan(angleRad)); System.out.println("atan2(4, 2) = " + Math.atan2(4, 2));

输出：

sin(30°) = 0.49999999999999994 cos(30°) = 0.8660254037844387 tan(30°) = 0.5773502691896257 atan2(4, 2) = 1.1071487177940904

有了这些基石，你可构建稳健科学计算器、执行工程计算、或自信处理地理坐标。