您有两种选择：
1）抽象工厂：
RectangularShape extends Shape
RoundShape extends Shape
并RectangularShapeFactory与RoundShapeFactory
2）构建器（另请参见有效Java中的第2项）
public Shape {
private final int x;
private final int y;
private final double radius;
private Shape(Builder builder) {
x = builder.x;
y = builder.y;
radius = builder.radius;
}
public static class Builder {
private final int x;
private final int y;
private double radius;
public Builder(int x, int y) {
this.x = x;
this.y = y;
}
public Builder radius(double radius) {
this.radius = radius;
return this;
}
public Shape build() {
return new Shape(this);
}
}
}
//in client code
Shape rectangle = new Shape.Builder(x,y).build();
Shape circle = new Shape.Builder(x,y).radius(radiusValue).build();
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