java问题，请求各位大神帮助我这个java初学者

[weixin_41973264]

package staticinnerclass;
import java.util.*;
class StaticInnerClassDemo
{
public static void main(String[] args)
{
Scanner in=new Scanner(System.in);
int num=in.nextInt();
double[] arr=new double[num];
for(double v:arr)
v=in.nextDouble();
ArraySort.Pair p=ArraySort.getPair(arr);
System.out.println("max="+p.getFirst());
System.out.println("min="+p.getLast());
}
}
class ArraySort
{
public static class Pair
{
private double first;
private double last;
public Pair(double first,double last){
this.first=first;
this.last=last;
}
public double getFirst(){
return first;
}
public double getLast(){
return last;
}
}
public static Pair getPair(double[] arr){
if(arr==null)
throw new NullPointerException("指针传递异常");
double max=arr[0]; //
double min=arr[0];
System.out.println(max+" "+min);
for(double v:arr){
if(v>max) max=v;
if(min<v) min=v;
}
return new Pair(max,min);
}
}

[我想再坚持一下]

你这初学者 起点不低

[qq_32427077]

出现什么问题了也不说

[moonwindlight]

这提问水平还得加强啊，看不出是啥问题？ 学会提问

[qq593467574]

代码错误我写在下面注释里了

class StaticInnerClassDemo {
	public static void main(String[] args) {
		Scanner in = new Scanner(System.in);
		int num = in.nextInt();
		double[] arr = new double[num];
//		for (double v : arr) //for each 不能赋值！
//			v = in.nextDouble();
		for(int i=0;i<arr.length;i++){
			arr[i]=in.nextDouble();
		}
		System.out.println(Arrays.toString(arr));
		ArraySort.Pair p = ArraySort.getPair(arr);
		System.out.println("max=" + p.getFirst());
		System.out.println("min=" + p.getLast());
	}
}

class ArraySort {
	public static class Pair {
		private double first;
		private double last;

		public Pair(double first, double last) {
			this.first = first;
			this.last = last;
		}

		public double getFirst() {
			return first;
		}

		public double getLast() {
			return last;
		}
	}

	public static Pair getPair(double[] arr) {
		if (arr == null)
			throw new NullPointerException("指针传递异常");
		double max = arr[0]; //
		double min = arr[0];
		System.out.println(max + "    " + min);
		
		for (double v : arr) {
			if (v > max)
				max = v;
			//if (min < v) 这个写反了
			if (v < min)
				min = v;
		}

		return new Pair(max, min);
	}
}

[miaoch]

for(double v:arr) v=in.nextDouble();
这个相当于
double v = arr[i];
v = 1;
v是基本类型，基本类型存值，你改变v的值，对arr[i] 没什么影响

[miaoch]

其实哪怕你用的是Double也是不行的，因为Double v和 arr[i] 会是两个引用，
当你v = nextDouble,会将v指向新的对象，对arr[i] 还是没半毛钱影响

[天行归来]

问题有两个，一个是没有给数组赋值；第二个问题是排序的时候，获取最小值运算符逻辑错了。

import java.util.*;

class StaticInnerClassDemo{
	public static void main(String[] args){
		Scanner in=new Scanner(System.in);
		int num=in.nextInt();
		double[] arr=new double[num];
		for(int i=0; i<num; i++){
			double v=in.nextDouble();
			arr[i] = v;
		}
		ArraySort.Pair p=ArraySort.getPair(arr);
		System.out.println("max="+p.getFirst());
		System.out.println("min="+p.getLast());
	}
}

class ArraySort {
	public static class Pair{
		private double first;
		private double last;

		public Pair(double first, double last) {
			this.first = first;
			this.last = last;
		}

		public double getFirst() {
			return first;
		}

		public double getLast() {
			return last;
		}
	}

	public static Pair getPair(double[] arr) {
		if (arr == null)
			throw new NullPointerException("指针传递异常");
		double max = arr[0]; //
		double min = arr[0];
		System.out.println(max + "    " + min);
		for (double v : arr) {
			if (v > max)
				max = v;
			if (min > v)
				min = v;
		}
		return new Pair(max, min);
	}
}