函数式编程处理加减法和空值处理
import java.math.BigDecimal;
public class TestCalculator<T> {
/**
* 汇总结果对象
*/
private final T collect;
private TestCalculator(T collect) {
this.collect = collect;
}
/**
* Wrap a collect to store the math result
*
* @param collect 汇总对象
* @return 汇总计算器
* @param <T> 汇总结果存放对象
*/
public static <T> TestCalculator<T> of(T collect) {
return new TestCalculator<>(collect);
}
public <P> TestCalculator<T> setIt(SetterFunction<T, P> setter, P p) {
setter.apply(collect, p);
return this;
}
/**
* 对象属性加法
*
* @param setter property setter function of {@link #collect}
* @param mapper property getter function of value convert
* @param right 加法项
*/
public TestCalculator<T> addInt(SetterFunction<T, Integer> setter,
GetterFunction<T, Integer> mapper, Integer right) {
addInt(setter, mapper.apply(collect), right);
return this;
}
/**
* 判断属性是否为空
*/
public TestCalculator<T> checkPropertyIsEmpty(TestFunc.GetterFunction<T, Object> mapper) {
Object apply = mapper.apply(collect);
if(null == apply) system.out.println("属性为空");
return this;
}
/**
* 对象属性加法
*
* @param setter property setter function of {@link #collect}
* @param left 加法左项
* @param right 加法右项
*/
public TestCalculator<T> addInt(SetterFunction<T, Integer> setter,
Integer left, Integer right) {
Integer result = null;
if (null != left || null != right) {
result = (null == left ? 0 : left) + (null == right ? 0 : right);
}
setter.apply(collect, result);
return this;
}
/**
* 对象属性减法
*
* @param setter property setter function of {@link #collect}
* @param mapper 被减数，property getter function of value convert
* @param right 减数
*/
public TestCalculator<T> subtractInt(SetterFunction<T, Integer> setter,
GetterFunction<T, Integer> mapper, Integer right) {
subtractInt(setter, mapper.apply(collect), right);
return this;
}
/**
* 对象属性减法
*
* @param setter property setter function of {@link #collect}
* @param left 被减数
* @param right 减数
*/
public TestCalculator<T> subtractInt(SetterFunction<T, Integer> setter,
Integer left, Integer right) {
Integer result = null;
if (null != left || null != right) {
result = (null == left ? 0 : left) - (null == right ? 0 : right);
}
setter.apply(collect, result);
return this;
}
/**
* 对象属性加法
*
* @param setter property setter function of {@link #collect}
* @param mapper property getter function of value convert
* @param right 加法项
*/
public TestCalculator<T> addBigDecimal(SetterFunction<T, BigDecimal> setter,
GetterFunction<T, BigDecimal> mapper, BigDecimal right) {
addBigDecimal(setter, mapper.apply(collect), right);
return this;
}
/**
* 对象属性加法
*
* @param setter property setter function of {@link #collect}
* @param left 加法左项
* @param right 加法右项
*/
public TestCalculator<T> addBigDecimal(SetterFunction<T, BigDecimal> setter,
BigDecimal left, BigDecimal right) {
BigDecimal result = null;
if (null != left || null != right) {
result = new BigDecimal(0);
if (null != left) {
result = result.add(left);
}
if (null != right) {
result = result.add(right);
}
}
setter.apply(collect, result);
return this;
}
/**
* 对象属性减法
*
* @param setter property setter function of {@link #collect}
* @param mapper 被减数，property getter function of value convert
* @param right 减数
*/
public TestCalculator<T> subtractBigDecimal(SetterFunction<T, BigDecimal> setter,
GetterFunction<T, BigDecimal> mapper, BigDecimal right) {
subtractBigDecimal(setter, mapper.apply(collect), right);
return this;
}
/**
* 对象属性减法
*
* @param setter property setter function of {@link #collect}
* @param left 被减数
* @param right 减数
*/
public TestCalculator<T> subtractBigDecimal(SetterFunction<T, BigDecimal> setter,
BigDecimal left, BigDecimal right) {
BigDecimal result = null;
if (null != left || null != right) {
result = new BigDecimal(0);
if (null != left) {
result = result.add(left);
}
if (null != right) {
result = result.subtract(right);
}
}
setter.apply(collect, result);
return this;
}
public T result() {
return collect;
}
@FunctionalInterface
public static interface GetterFunction<T, R> {
R apply(T t);
}
@FunctionalInterface
public static interface SetterFunction<T, P> {
void apply(T t, P p);
}
}
测试类
public class test {
public static void main(String[] args) {
User user = new User();
user.setName("xxx");
TestFunc.of(user)
.checkPropertyIsEmpty(User::getName)
.checkPropertyIsEmpty(User::getAge);
}
}
class User {
private String name;
private Integer age;
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
public Integer getAge() {
return age;
}
public void setAge(Integer age) {
this.age = age;
}
}
输出结果
邯城往事