Setter - 检查值

Question

我应该检查该值，如果不是该值，我不会更新该值。如果输入有效，那么我将返回它。最小可重现示例：public class Student {    private int studentId;    private String name;    private double grade;    private double multiplier;    public double getMultiplier() {        return multiplier;    }    /**     * The setter for the multiplier must check that the value is either 1.08 *     * 1.06 or 1.08 or 1.06     *      * If not, then do not update the value     *      * @param multiplier     * @return if the input was valid     */     public boolean setMultiplier(double multiplier) {         if( multiplier == 1.08 * 1.06 || multiplier == 1.08 || multiplier == 1.06 ) { }         return multiplier;    }    ...}

Answer 1

public void setMultiplier(double multiplier) { // method head

    if (multiplier == 1.08 * 1.06 || multiplier == 1.08 || multiplier == 1.06) {

        this.multiplier = multiplier; // here the field variable is overwritten

    }

    throw new IllegalArgumentException("exception message");

}

你忘了写你的类的字段变量。

setter 应该覆盖字段变量。setter 应该覆盖字段变量。他没有返回任何内容，因此在方法头中返回 void 而不是 boolean 。如果参数错误，抛出异常（尽可能有意义）。

提示：我不会将 1.06 或 1.08 等常量分布在代码中的任何位置。您可以将其定义如下：

public class student {

    private static final double MEANINGFUL_NAME_0 = 1.06;

    private static final double MEANINGFUL_NAME_1 = 1.08;

    // other code below

}

优点：如有必要，您只需在一处更改常量。您错过并写 1.07 而不是 1.06 的可能性较低。

Answer 2

可能是常量的用例：

private static final double ONE_DOT_ZERO_SIX = 1.06f;

private static final double ONE_DOT_ZERO_EIGHT = 1.08f;

/**

 * Just to know if it is valid

 */

public boolean setMultiplier(double multiplier) {

    return (multiplier == ONE_DOT_ZERO_SIX || multiplier == ONE_DOT_ZERO_EIGHT

            || multiplier == (ONE_DOT_ZERO_SIX * ONE_DOT_ZERO_EIGHT));

}

/**

 * Return the multiplier if it is valid, otherwise 1

 */

public double setMultiplier(double multiplier) {

    if (multiplier == ONE_DOT_ZERO_SIX || multiplier == ONE_DOT_ZERO_EIGHT

            || multiplier == (ONE_DOT_ZERO_SIX * ONE_DOT_ZERO_EIGHT)) {

        return multiplier;

    } else {

        // return any invalid multiplier, this one doesn't change values at least

        return 1;   

    }

}

/**

 * Set the correct multiplier or a substitute

 */

public void setMultiplier(double multiplier) {

    if (multiplier == ONE_DOT_ZERO_SIX || multiplier == ONE_DOT_ZERO_EIGHT

            || multiplier == (ONE_DOT_ZERO_SIX * ONE_DOT_ZERO_EIGHT)) {

        this.multiplier = multiplier;

    } else {

        // return any invalid multiplier, this one doesn't change values at least

        this.multiplier = 1;

    }

}

Answer 3

Asetter应该更新一个值，并且不返回值（getter的角色），因此它的返回类型应该是void而不是boolean

public void setMultiplier(double multiplier) {

    if( multiplier == 1.08 * 1.06 || multiplier == 1.08 || multiplier == 1.06 ) {

        this.multiplier = multiplier; 

    }

}

Answer 4

我认为您只是忘记实际设置新值。

因此，如果你这样做，它应该可以工作：

public void setMultiplier(double multiplier) {

    if( multiplier == 1.08 * 1.06 || multiplier == 1.08 || multiplier == 1.06 ) {

        this.multiplier = multiplier;

    }

}

此外，setter 通常void不是布尔值，并且没有返回值。