Java方法及数组相关原理解析

public static void main(String[] args) {
    for (int i=0;i<args.length;i++){
      System.out.println("args["+i+"]:"+args[i]);
    }
  }//传递命令行参数给main函数

public static void main(String[] args) {
    //调用
    printMax(34,3,3,2,56.5);
    printMax(new double[]{1,2,3});
  }

  public static void printMax(double... numbers){//可变参数
    if (numbers.length==0){
      System.out.println("No argument passed");
      return;
    }

    double result=numbers[0];

    //排序
    for (int i = 1; i < numbers.length; i++) {
      if(numbers[i]>result){
        result=numbers[i];
      }
    }
    System.out.println("The max value is "+result);
  }

public static int f(int n){
    if(n==1){
      return 1;
    }else {
      return n*f(n-1);
    }
  }

//反转数组
	public static int[] reverse(int[] arrays){
    int[] result = new int[arrays.length];
    for (int i = 0,j=result.length-1; i <arrays.length ; i++,j--) {
      result[j]=arrays[i];
    }
    return result;
  }

  public static int[] sort(int[] array){
//   冒泡排序
    int temp=0;
    for (int i = 0; i < array.length-1; i++) {
      for (int j = 0; j < array.length-1-i; j++) {//i表示已经排好的数字个数，所以在内层循环时减去i，减少比较次数
        if(array[j+1]<array[j]){
          temp=array[j];
          array[j]=array[j+1];
          array[j+1]=temp;
        }
      }
    }
    return array;
  }

//看代码才能看懂
  public static void main(String[] args) {
    //稀疏数组
    int[][] array1=new int[11][11];
    array1[1][2]=1;
    array1[2][3]=2;

    System.out.println("输出原始数据：");

    for (int[] ints:array1) {
      for(int anint:ints){
        System.out.print(anint+"\t");
        //输出原始数组
      }
      System.out.println();
    }
    System.out.println("================");
    //转换为稀疏数组
    //获取数组中有效值
    int sum= 0;
    for (int i = 0; i < 11; i++) {
      for (int j = 0; j < 11; j++) {
        if(array1[i][j]!=0){
          sum++;
        }
      }
    }
    System.out.println("有效值个数："+sum);

    //创建稀疏数组
    int[][] array2=new int[sum+1][3];
    array2[0][0]=11;
    array2[0][1]=11;
    array2[0][2]=sum;
    //遍历二维数组，将有效值存在稀疏数组中
    int count=0;
    for (int i = 0; i < array1.length; i++) {
      for (int j = 0; j < array1[i].length; j++) {//二维数组每一行的长度
        //形成稀疏数组
        if(array1[i][j]!=0){
          count++;
          array2[count][0]=i;
          array2[count][1]=j;
          array2[count][2]=array1[i][j];
        }
      }
    }
    //输出稀疏数组
    System.out.println("稀疏数组");

    for (int i = 0; i < array2.length; i++) {
      System.out.println(array2[i][0]+"\t"
          +array2[i][1]+"\t"
          +array2[i][2]+"\t");
    }

    System.out.println("================");
    System.out.println("还原");
    int[][] array3=new int[array2[0][0]][array2[0][1]];

    //还原值
    for (int i = 1; i < array2.length; i++) {
      //在还原数组中将坐标与值相对应
      array3[array2[i][0]][array2[i][1]]=array2[i][2];
    }

    //打印输出
    System.out.println("输出还原数组：");

    for (int[] ints:array3) {
      for(int anint:ints){
        System.out.print(anint+"\t");
        //输出还原数组
      }
      System.out.println();
    }
  }