目录:
1,声明数组；
2,初始化数组；
3,查看数组长度；
4,遍历数组；
5,int数组转成string数组；
6,从array中创建arraylist；
7,数组中是否包含某一个值；
8,将数组转成set集合；
9,将数组转成list集合；
10,Arrays.fill()填充数组；
11,数组排序；
12,复制数组；
13,比较两个数组；
14,去重复；
15,查询数组中的最大值和最小值；
1,声明数组:
String [] arr;
int arr1[];
String[] array=new String[5];
int score[]=new int[3];
2,初始化数组:
//静态初始化
int arr2[]=new int[]{1,2,3,4,5};
String[] array1={"老大","老二","老三","老四","老五"};
String[] array2=new String[]{"黄渤","张艺兴","孙红雷","小猪","牙哥","黄磊"};
int score[]=new int[3];
//动态初始化
for(int i=0;i<score.length;i++) {
score[i]=i+1;
}
3,查看数组长度
int length=array1.length;
System.out.println("length： "+array1.length);
4.遍历数组
for (int i = 0; i < array1.length; i++) {
System.out.println(array1[i]);
}
5.int数组转成string数组
int[] array3={1,2,3,4,5,6,7,8,9,0};
String arrStrings=Arrays.toString(array3);
System.out.println(arrStrings);
6.从array中创建arraylist
ArrayList<String> arrayList=new ArrayList<String>(Arrays.asList(array1));
System.out.println(arrayList);
7.数组中是否包含某一个值
String a = "小李";
String[] array = {"小李","小张","小明"};
if (Arrays.asList(array).contains(a)) {
System.out.println("小李在这儿");
}
8.将数组转成set集合
String[] array2=new String[]{"黄渤","张艺兴","孙红雷","小猪","牙哥","黄磊"};
Set<String> set=new HashSet<String>(Arrays.asList(array2));
System.out.println(set);
9.将数组转成list集合
String[] array2=new String[]{"黄渤","张艺兴","孙红雷","小猪","牙哥","黄磊"};
//方法 1.
List<String> list=new ArrayList<String>();
for (int i = 0; i < array2.length; i++) {
list.add(array2[i]);
}
String[] arrStrings2={"1","2","3"};
//方法 2.
List<String > list2=java.util.Arrays.asList(arrStrings2);
System.out.println(list2);
10.Arrays.fill()填充数组
int[] arr3=new int[5];
Arrays.fill(arr3, 10); //将数组全部填充10
//遍历输出
for (int i = 0; i < arr3.length; i++) {
System.out.println(arr3[i]);
}
11.数组排序
//方法 1.
int[] arr4 = {3, 7, 2, 1, 9};
Arrays.sort(arr4); //.sort(int[] a) 放入数组名字
for (int i = 0; i < arr4.length; i++) {
System.out.println(arr4[i]);
}
//方法 2.
int[] arr5 = {3, 7, 2, 1, 9,3,45,7,8,8,3,2,65,34,5};
Arrays.sort(arr5, 1, 4); //.sort(a, fromIndex, toIndex) 从第几个到第几个之间的进行排序
for (int i = 0; i < arr5.length; i++) {
System.out.println(arr5[i]);
}
12.复制数组
//方法 1.
int[] arr6 = {3, 7, 2, 1};
int[] arr7=Arrays.copyOf(arr6, 10); //指定新数组的长度
//方法 2.
int[] arr8=Arrays.copyOfRange(arr6, 1, 3); //只复制从索引[1]到索引[3]之间的元素（不包括索引[3]的元素）
for (int i = 0; i < arr8.length; i++) {
System.out.println(arr8[i]);
}
13.比较两个数组
int[] arr9 = {1, 2, 3, 4,5,6,7,8,9,0};
boolean arr10=Arrays.equals(arr6, arr9);
System.out.println(arr10);
14.去重复
int[] arr11 = {1, 2, 3, 4,5,6,7,8,9,0,3,2,4,5,6,7,4,32,2,1,1,4,6,3};
//利用set的特性
Set<Integer> set2=new HashSet<Integer>();
for (int i = 0; i < arr11.length; i++) {
set2.add(arr11[i]);
}
System.out.println(set2);
int[] arr12 = new int[set2.size()];
int j=0;
for (Integer i:set2) {
arr12[j++]=i;
}
System.out.println(Arrays.toString(arr12));
15.查询数组中的最大值和最小值
int[] arr11 = {10, 2, 3, 4,5,6,7,8,9,0,3,2,4,5,6,7,4,32,2,1,1,4,6,3};
//计算最大值
int max = arr11[0];
for (int i = 1; i < arr11.length; i++) {
if (arr11[i] > max) {
max = arr11[i];
}
}
System.out.println("Max is " + max);
//计算最小值
int min = arr11[0];
for (int i = 0; i < arr11.length; i++) {
if (arr11[i]<min) {
min = arr11[i];
}
}
System.out.println("Min is " + min);
16foreach循环
JDK 1.5 引进了一种新的循环类型，被称为 foreach 循环或者加强型循环，它能在不使用下标的情况下遍历数组。
double[] myList = {1.9, 2.9, 3.4, 3.5};
// 打印所有数组元素
for (double element: myList) {
System.out.println(element);
}
