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booleanpublic 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。