Java三元运算符（？:)不起作用;第二个或第三个操作数返回布尔值 [英] Java ternary operator (?:) doesn't work; second or third operand return boolean

问题描述

有人能告诉我为什么三元运算符的使用不正确吗？操作数2和3返回一个布尔值。

Can someone tell me why this use of the ternary operator is incorrect? Operands 2 and 3 return a boolean.

public class Something {
...
private static final double REFERENCE_FRAME_MID_X = 0;
private static final double REFERENCE_FRAME_MID_Y = 0;

private boolean findInsideOrOutsideGeneralEllipse(Point2D destCirclePos) {
    List<Boolean> returnValue = new ArrayList<>();
    Point2D referenceFrameCenter = new Point2D.Double(REFERENCE_FRAME_MID_X, REFERENCE_FRAME_MID_Y);
    Ellipse2D insideAreaEllipse2D = getEllipse2D(referenceFrameCenter.getX(), referenceFrameCenter.getY(),
                                                    destCirclePos.distance(referenceFrameCenter));

    // doesn't work
    insideAreaEllipse2D.contains(destCirclePos) ? returnValue.add(true) : returnValue.add(false);

    // works
    if (insideAreaEllipse2D.contains(destCirclePos)) {
        returnValue.add(true);
    } else {
        returnValue.add(false);
    }
}
...
}

推荐答案

Java三元操作条件的使用应该类似于

Usage of Java ternary operation condition should looks like

result = testCondition ? value1 : value2

它是java语言规范。

it's java-language specification.

平等，关系和条件运算符

在以下示例中，
此运算符应该读作：如果 someCondition 是 true ，请将 value1 的
值分配给结果。否则，赋值 value2 到
结果

In the following example, this operator should be read as: "If someCondition is true, assign the value of value1 to result. Otherwise, assign the value of value2 to result

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