如果我们有不同的参数，是否有任何快捷方式来增加值的总和？

Question

我有以下代码，在这个DemoClass中分别有val1、val2、val3和val4的getter和setter，如果列表中有多个值，我想添加每个值。例如：在第一次迭代val11=10000，第二次迭代val12=2000等等。现在我想要一个结果为val11 val12的解决方案，这应该适用于每个值，即val1、val2、val3和val4。

List<DemoClass> list= new ArrayList<DemoClass>();    
int count=1;
for (Iterator iterator = list.iterator(); iterator.hasNext();) {
    DemoClass cls = (DemoClass) iterator.next();
    parameter.put("val1"+count, cls.getVal1());
    parameter.put("val2"+count, cls.getVal2());
    parameter.put("val3"+count, cls.getVal3());
    parameter.put("val4"+count, cls.getVal4());
    count++;
}

DemoClass。Java语言

public class DemoClass{
private String val1;
private String val2;
private String val3;
private String val4;

public String getVal1() {
    return val1;
}

public void setVal1(String val1) {
    this.val1= val1;
}

public String getVal2() {
    return val2;
}

public void setVal2(String val2) {
    this.val2= val2;
}

public String getVal3() {
    return val3;
}

public void setVal3(String val3) {
    this.val3= val3;
}

public String getval4() {
    return val4;
}
public void setVal4(String val4) {
    this.val4= val4;
}

}

Answer 1

如果要获取每个值（val1、val2、val3和val4）中都包含的单个DemoClass实例，则如果您使用的是JAVA 8或更高版本（流API），则输入中DemoClass列表中对应属性的整数值之和将有助于此代码

public static DemoClass calcul(List<DemoClass> list) {
    DemoClass demoClass = new DemoClass();
    return list.stream().reduce(demoClass, (acc, curr) -> {
        DemoClass tmp = new DemoClass();
        tmp.setVal1(String.valueOf(Integer.parseInt(acc.getVal1()) + Integer.parseInt(curr.getVal1())));
        tmp.setVal2(String.valueOf(Integer.parseInt(acc.getVal2()) + Integer.parseInt(curr.getVal2())));
        tmp.setVal3(String.valueOf(Integer.parseInt(acc.getVal3()) + Integer.parseInt(curr.getVal3())));
        tmp.setVal4(String.valueOf(Integer.parseInt(acc.getVal4()) + Integer.parseInt(curr.getVal4())));
        return tmp;
    });
}

更新：

对于JAVA 7的解决方案，您需要添加所有参数构造函数

public static DemoClass calcul(List<DemoClass> list) {
    DemoClass demoClass = new DemoClass("0", "0", "0", "0");
    for(DemoClass curr : list) {
        demoClass.setVal1(String.valueOf(Integer.parseInt(demoClass.getVal1()) + Integer.parseInt(curr.getVal1())));
        demoClass.setVal2(String.valueOf(Integer.parseInt(demoClass.getVal2()) + Integer.parseInt(curr.getVal2())));
        demoClass.setVal3(String.valueOf(Integer.parseInt(demoClass.getVal3()) + Integer.parseInt(curr.getVal3())));
        demoClass.setVal4(String.valueOf(Integer.parseInt(demoClass.getVal4()) + Integer.parseInt(curr.getVal4())));
    }
    return demoClass;
}

要获取参数Map：