Java~数组

数组常用方法

//声明数组
String [] arr;
int arr1[];
String[] array=new String[5];
int score[]=new int[3];

//初始化数组
//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; 
}

//查看数组长度
int length=array1.length;
System.out.println("length："+array1.length);

//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);

//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";
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");
}

//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);

//将数组转成list集合
String[] array3=new String[]{"大黑","大白","大红","大紫","大蓝","大黄"};
//方法 1.
List<String> list=new ArrayList<String>();
for (int i = 0; i < array3.length; i++) {
    list.add(array3[i]);
}
String[] arrStrings2={"1","2","3"};
//方法 2.
List<String > list2=java.util.Arrays.asList(arrStrings2);
System.out.println(list2);

//Arrays.fill()填充数组
int[] arr3=new int[5];
//将数组全部填充10
Arrays.fill(arr3, 10);  
//遍历输出
for (int i = 0; i < arr3.length; i++) {
	System.out.println(arr3[i]);
}

//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]);
}

//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]);
}

//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
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));

//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);

定义二维数组

public static void main(String args[]) {
    //此时的数组并不是一个等列数组
    int data[][] = new int[][] {{1, 2, 3}, {4, 5}, {6, 7, 8, 9}};
    //如果在进行输出的时候一定要使用双重循环，
    //外部的循环控制输出的行数，而内部的循环控制输出列数
    for(int i = 0; i < data.length; i++) {
	for(int j = 0; j < data[i].length; j++) {
	   System.out.print("data[" + i + "][" + j + "]=" + data[i][j] + "、");
	}
	   System.out.println();
    }
}