java定义数组与遍历数组以及数组的常用方法

一、定义静态数组

		Student students[]=new Student[3];
		students[0]=new Student("张三",10);
		students[1]=new Student("李四",11);
		students[2]=new Student("王五",12);

java forEach遍历上面的静态数组

            for(Student s:students){
			System.out.println(s);
	     	}

二、定义动态数组

	                Object[] X = null;
		        Object[] Y = null;
			String sql1 = "select t.* from place t";
			List<IBean> points =query(sql1, covergeId);
			 X = new Object[points.size()];
			 Y = new Object[points.size()];
			for(int j=0;j<points.size();j++){
			 pointX[j]=points.get(j).get("X");
			 pointY[j]=points.get(j).get("Y");
			}

往数组中动态添加元素

String [] sqls = new String[sheet.getLastRowNum()];
condictionSql = "INSERT INTO "+templateTable+"("+paramkey.toString()+")  VALUES( "+paramval.toString()+")";
}
sqls[i-1] = condictionSql;

for循环遍历上面的数组

for(int i=0;i<sqls.length;i++){
system.out.print(sqls[i]+"");
}

三、java通过split方法截取字符串来获得数组

String[] split = joinId.split(",");

	                String location = glEmerg.getLOCATION();
			String[] str = location.split(",");
			String Xstr = str[0];
			String Ystr = str[1];
			String[] arr=new String[]{Xstr,Ystr};
			
			String newLocation = String.join(",",arr);

String.join()方法:String.join()是JDK8新增方法(无需引包）字符串类型的数组推荐使用，将数组以某拼接符拼接到一起形成新的字符串。

java通过join()把数组转为字符串

List<String> members =  new ArrayList<String>(Arrays.asList(activity.getMembers().split(",")));
		members.addAll(orgUserIds);
		members = new ArrayList<>(new HashSet<>(joinMembers));
		if(CollectionUtils.isEmpty(members))
		{
			return "";
		}
		return String.join(",", members);

借助传统的Collection的遍历方法

String[] strings = {"A"， "B"， "C"， "D"};  
Collection stringList = java.util.Arrays.asList(strings);  
/* 开始遍历 */  
for (Iterator itr = stringList.iterator(); itr.hasNext();) {  
Object str = itr.next();  
System.out.println(str);  
}  
/* 依次输出“A”、“B”、“C”、“D” */  

数组的基本方法

	public static void main(String[] args) {
		int arr[]={1,7,3,8,2};
		System.out.println(arr);
		System.out.println("以字符串形式输出数组："+Arrays.toString(arr));
		Arrays.sort(arr); // 给数组排序
		System.out.println("排序后的数组："+Arrays.toString(arr));
		System.out.println(Arrays.binarySearch(arr, 1));
		Arrays.fill(arr, 0); // 将指定内容填充到数组中
		System.out.println("填充数组后的字符串："+Arrays.toString(arr));
		
	}

利用Arrays工具类中的toString静态方法可以将一维数组转化为字符串形式并输出。