Scala集合Seq-Api
先上一张Scala接口架构图:
下面主要是Seq的Api用例：
创建共用的Seq:
val s1 = Seq(1,2,3,4,5)
val s2 = Seq(6,7,8,9,10)
索引和长度
//获取某个下标的值
//res0: Int = 2
s1(1)
s1.apply(1)
//是否包括该下标，下标从0开始，
//结果 res0: Boolean = true
s1.isDefinedAt(1)
//seq长度，结果:res0: Int = 5
s1.length
//seq长度比n大则返回+1，比n少则返回-1，=n则返回0
s1.lengthCompare(5)
//返回0--(s1.length-1) 的Range
//结果: res0: scala.collection.immutable.Range = Range 0 until 5
s1.indices
查询下标
//查询元素1所在的下标
//结果 res0: Int = 0
s1.indexOf(1)
//查找该元素的最后一个索,res0: Int = 2
val s3 = Seq(1,2,2,4,5,2,2,4)
s3.lastIndexOf(2)
//右边seq在左边seq的开始匹配索引
//结果:res0: Int = 1
val s4 = Seq(2,2,4)
s3.indexOfSlice(s4)
////右边seq在左边seq的最后匹配索引
//结果:res0: Int = 5
s3.lastIndexOfSlice(s4)
//查找第一个满足条件的索引
//结果:res0: Int = 3
s3.indexWhere(_ > 2)
//从seq(n)开始，连续满足条件的个数
//结果:res0: Int = 2
s3.segmentLength(_ > 2,3)
//从seq(0)开始，连续满足条件的个数
//res0: Int = 8
s3.prefixLength(_ > 0)
添加
//把n加入到集合在头部
//结果：res0: Seq[Int] = List(6, 1, 2, 3, 4, 5)
6 +: s1
//把n加到集合后面
//结果:res0: Seq[Int] = List(1, 2, 3, 4, 5, 6)
s1 :+ 6
//第一个参数len,第二个参数value,如果集合长度达<len,则将集合扩展到len,并用value填充。否则什么都不做
//结果:res0: Seq[Int] = List(1, 2, 3, 4, 5, 2, 2)
s1 padTo (7,2)
更新
//从下标为2[index]的元素开始，用集合s2所有元素替换掉1[n]个数。
//结果:res0: Seq[Int] = List(1, 2, 6, 7, 8, 9, 10, 4, 5)
s1.patch(2,s2,1)
//更新下标i的值
//结果:res0: Seq[Int] = List(1, 2, 10, 4, 5)
s1.updated(2,10)
排序
val s3 = Seq(4,2,5,8,3,0)
//按自然升序排
//结果:res0: Seq[Int] = List(0, 2, 3, 4, 5, 8)
s3.sorted
//按自定义函数排序
//结果:res0: Seq[Int] = List(8, 5, 4, 3, 2, 0)
s3.sortWith((x,y) => x > y)
//从大到小,结果:res0: Seq[Int] = List(8, 5, 4, 3, 2, 0)
s3.sortBy(x => -x)
//从小到大，结果:res0: Seq[Int] = List(0, 2, 3, 4, 5, 8)
s3.sortBy(x => x)
反转
//把集合反转，结果:res0: Seq[Int] = List(5, 4, 3, 2, 1)
s1.reverse
//返回反转后的集合迭代器
//结果:54321
val it = s1.reverseIterator
while (it.hasNext) {
print(it.next())
}
//反转集合，按指定函数进行map
//结果:res0: Seq[Int] = List(6, 5, 4, 3, 2)
s1.reverseMap(x => x + 1)
比较
val s3 = Seq(1,2,3)
//判断是否以另一个集合开始,元素和顺序一致
//结果:res0: Boolean = true
s1.startsWith(s3)
//判断是否以另一个集合结尾，元素和顺序一致
//结果:res0: Boolean = true
val s4 = Seq(3,4,5)
s1.endsWith(s4)
//判断集合是否包含某个元素
//结果:res0: Boolean = true
s1.contains(2)
//判断是否包含另一个集合的连续字段
//结果:res0: Boolean = true
s1.containsSlice(s3)
//判断两个集合长度，按下标遍历，满足输入函数的返回true，不满足的返回false
//结果:res0: Boolean = true
val s5 = Seq(1,2,3,4,5)
s1.corresponds(s5)((x,y)=>x == y)
多集合操作
val s3 = Seq(0,1,2,3,4)
//获取两个集合的交集
//结果:res0: Seq[Int] = List(1, 2, 3, 4)
s1.intersect(s3)
//获取第一个集合有，第二个集合没有的
//结果:res0: Seq[Int] = List(5)
s1.diff(s3)
//两个集合合并
//结果：res0: Seq[Int] = List(1, 2, 3, 4, 5, 0, 1, 2, 3, 4)
s1.union(s3)
//集合去重
//结果:res0: Seq[Int] = List(1, 2, 3, 4)
val s4 = Seq(1,1,2,3,2,3,4)
s4.distinct
可变集合 添加
val buffer = mutable.Buffer(1,2,3,4,5)
val b2 = mutable.Buffer(7,8)
//向buffer增加一个元素
//结果:res0: scala.collection.mutable.Buffer[Int] = ArrayBuffer(1, 2, 3, 4, 5, 6)
buffer += 6
//向buffer增加几个元素
//结果:res0: scala.collection.mutable.Buffer[Int] = ArrayBuffer(1, 2, 3, 4, 5, 7, 8, 9)
buffer += (7,8,9)
//添加集合
//结果:res0: scala.collection.mutable.Buffer[Int] = ArrayBuffer(1, 2, 3, 4, 5, 7, 8)
buffer ++= b2
//把元素放在集合头部
//结果:res0: scala.collection.mutable.Buffer[Int] = ArrayBuffer(6, 1, 2, 3, 4, 5)
6 +=: buffer
//把集合放buffer头部
//结果:res0: scala.collection.mutable.Buffer[Int] = ArrayBuffer(7, 8, 1, 2, 3, 4, 5)
b2 ++=: buffer
//在下标i，插入元素
//结果:1210345
buffer.insert(2,10)
//从下标开始插入整个数组
//结果:12789345
val arr = Array(7,8,9)
buffer.insertAll(2,arr)
可变集合 删除
val buffer = mutable.Buffer(1,2,3,4,5)
//删除指定下标的元素
//结果: 1245
buffer.remove(2)
//从指定下标开始，删除n个元素
//结果:125
buffer.remove(2,2)
//从指定下标开始截取
//结果:345
buffer.trimStart(2)
//从下标0截取到指定下标
//结果:123
buffer.trimEnd(2)
//清空数据
buffer.clear()