总结所有元素java arraylist
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Sum all the elements java arraylist
提问by
If I had: ArrayList<Double> m = new ArrayList<Double>();with the double values ??inside, how should I do to add up all the ArrayList elements?
如果我有：ArrayList<Double> m = new ArrayList<Double>();在里面有双精度值，我应该怎么做才能把所有的 ArrayList 元素加起来？
public double incassoMargherita()
{
double sum = 0;
for(int i = 0; i < m.size(); i++)
{
}
return sum;
}
as?
作为？
采纳答案by Barranka
Two ways:
两种方式：
Use indexes:
使用索引：
double sum = 0;
for(int i = 0; i < m.size(); i++)
sum += m.get(i);
return sum;
Use the "for each" style:
使用“for each”样式：
double sum = 0;
for(Double d : m)
sum += d;
return sum;
回答by TheEwook
Not very hard, just use m.get(i)to get the value from the list.
不是很难，只是用来m.get(i)从列表中获取值。
public double incassoMargherita()
{
double sum = 0;
for(int i = 0; i < m.size(); i++)
{
sum += m.get(i);
}
return sum;
}
回答by j.jerrod.taylor
I haven't tested it but it should work.
我还没有测试过，但它应该可以工作。
public double incassoMargherita()
{
double sum = 0;
for(int i = 0; i < m.size(); i++)
{
sum = sum + m.get(i);
}
return sum;
}
回答by Lokeshkumar R
回答by Mikhail Kholodkov
Java 8+ version for Integer, Long, Doubleand Float
Java的8+版本Integer，Long，Double和Float
List<Integer> ints = Arrays.asList(1, 2, 3, 4, 5);
List<Long> longs = Arrays.asList(1L, 2L, 3L, 4L, 5L);
List<Double> doubles = Arrays.asList(1.2d, 2.3d, 3.0d, 4.0d, 5.0d);
List<Float> floats = Arrays.asList(1.3f, 2.2f, 3.0f, 4.0f, 5.0f);
long intSum = ints.stream()
.mapToLong(Integer::longValue)
.sum();
long longSum = longs.stream()
.mapToLong(Long::longValue)
.sum();
double doublesSum = doubles.stream()
.mapToDouble(Double::doubleValue)
.sum();
double floatsSum = floats.stream()
.mapToDouble(Float::doubleValue)
.sum();
System.out.println(String.format(
"Integers: %s, Longs: %s, Doubles: %s, Floats: %s",
intSum, longSum, doublesSum, floatsSum));
15, 15, 15.5, 15.5
15、15、15.5、15.5
