看到好的转来留着,随时学习。
目录:
- 声明数组;
- 初始化数组;
- 查看数组长度;
- 遍历数组;
- int数组转成string数组;
- 从array中创建arraylist;
- 数组中是否包含某一个值;
- 将数组转成set集合;
- 将数组转成list集合;
- Arrays.fill()填充数组;
- 数组排序;
- 复制数组;
- 比较两个数组;
- 去重复;
- 查询数组中的最大值和最小值;
- list的交集并集合集
备注:文内代码具有关联性。
1.声明数组;
1
2
3
4
|
String
[] arr; int arr1[]; String[]
array= new String[ 5 ]; int score[]= new int [ 3 ]; |
2.初始化数组;
1
2
3
4
5
6
7
8
9
10
|
//静态初始化 int arr2[]= new int []{ 1 , 2 , 3 , 4 , 5 }; String[]
array1={ "马超" , "马云" , "关羽" , "刘备" , "张飞" }; 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;
1
2
|
int length=array1.length; System.out.println( "length:
" +array1.length); |
4.遍历数组;
1
2
3
|
for ( int i
= 0 ;
i < array1.length; i++) { System.out.println(array1[i]); } |
5.int数组转成string数组;
1
2
3
|
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;
1
2
|
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;
1
2
3
4
5
|
String
a= "马超" ; String[]
array1={ "马超" , "马云" , "关羽" , "刘备" , "张飞" }; if (Arrays.asList(array1).contains(a))
{ System.out.println( "马超在这里" ); } |
8.将数组转成set集合;
1
2
3
|
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;
1
2
3
4
5
6
7
8
9
10
11
|
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;
1
2
3
4
5
6
|
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;
1
2
3
4
5
6
7
8
9
10
11
12
|
//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;
1
2
3
4
5
6
7
8
|
//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;
1
2
3
|
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;
1
2
3
4
5
6
7
8
9
10
11
12
13
|
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;
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
|
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); |
附:完整代码:
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
|
package MyTest01; import java.util.*; public class ArrayTest02
{ public static void main(String[]
args) { //声明数组 String
[] arr; int arr1[]; //初始化数组 int arr2[]= new int []{ 1 , 2 , 3 , 4 , 5 }; String[]
array1={ "马超" , "马云" , "关羽" , "刘备" , "张飞" }; String[]
array2= new String[]{ "黄渤" , "张艺兴" , "孙红雷" , "小猪" , "牙哥" , "黄磊" }; String[]
array= new String[ 5 ]; //查看数组的长度 int length=array1.length; System.out.println( "length:
" +array1.length); //输出数组 //
System.out.println(array1); //结果:[Ljava.lang.String;@32f22097 System.out.println( "arr2:
" +Arrays.toString(arr2)); //遍历数组 for ( int i
= 0 ;
i < array1.length; i++) { //
System.out.println(array1[i]); } //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); //从array中创建arraylist ArrayList<String>
arrayList= new ArrayList<String>(Arrays.asList(array1)); System.out.println(arrayList); //数组中是否包含某一个值 String
a= "马超" ; if (Arrays.asList(array1).contains(a))
{ System.out.println( "马超在这里" ); } //将数组转成set集合 Set<String>
set= new HashSet<String>(Arrays.asList(array2)); System.out.println(set); //将数组转成list集合 List<String>
list= new ArrayList<String>(); for ( int i
= 0 ;
i < array2.length; i++) { list.add(array2[i]); } String[]
arrStrings2={ "1" , "2" , "3" }; List<String
> list2=java.util.Arrays.asList(arrStrings2); System.out.println(list2); //Arrays.fill()填充数组 int []
arr3= new int [ 5 ]; Arrays.fill(arr3, 10 ); //将数组全部填充10 for ( int i
= 0 ;
i < arr3.length; i++) { System.out.println(arr3[i]); } //数组排序 int []
arr4 = { 3 , 7 , 2 , 1 , 9 }; Arrays.sort(arr4); for ( int i
= 0 ;
i < arr4.length; i++) { System.out.println(arr4[i]); } int []
arr5 = { 3 , 7 , 2 , 1 , 9 , 3 , 45 , 7 , 8 , 8 , 3 , 2 , 65 , 34 , 5 }; Arrays.sort(arr5, 1 , 4 ); //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]); } //复制数组 int []
arr6 = { 3 , 7 , 2 , 1 }; int []
arr7=Arrays.copyOf(arr6, 10 ); //指定新数组的长度 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]); } //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); //去重复 //利用set的特性 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 }; 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)); } } |
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
|
package MyTest01; public class ArrayTest03
{ public static void main(String[]
args) { 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); } } |
16.list的交集并集合集
package com;
import java.util.ArrayList;
import java.util.Iterator;
import java.util.List;
public class Test {
public static void main(String[] args) {
List list1 =new ArrayList();
list1.add("1111");
list1.add("2222");
list1.add("3333");
List list2 =new ArrayList();
list2.add("3333");
list2.add("4444");
list2.add("5555");
//并集
//list1.addAll(list2);
//交集
//list1.retainAll(list2);
//差集
//list1.removeAll(list2);
//无重复并集
list2.removeAll(list1);
list1.addAll(list2);
Iterator<String> it=list1.iterator();
while (it.hasNext()) {
System.out.println(it.next());
}
//System.out.println("-----------------------------------\n");
//printStr(list1);
}
public static void printStr(List list1){
for (int i = 0; i < list1.size(); i++) {
System.out.println(list1.get(i));
}
}
}