diff --git a/w4/Triangle.java b/w4/Triangle.java
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+++ b/w4/Triangle.java
@@ -0,0 +1,29 @@
+/**
+ * 三角形（已知底与高）：面积 = 底 * 高 / 2
+ */
+public class Triangle extends Shape {
+
+    private final double base;
+    private final double height;
+
+    public Triangle(double base, double height) {
+        if (base <= 0 || height <= 0) {
+            throw new IllegalArgumentException("底和高必须为正数");
+        }
+        this.base = base;
+        this.height = height;
+    }
+
+    public double getBase() {
+        return base;
+    }
+
+    public double getHeight() {
+        return height;
+    }
+
+    @Override
+    public double getArea() {
+        return base * height / 2.0;
+    }
+}
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