Java学习关于循环和数组练习题整理

whlie(条件语句) {
	循环体
}//先进行条件语句的判断，再进行循环体

do {
	循环体
}whlie （条件语句）//先执行一次循环后再进行条件语句的判断

//1+2+3+...+n<1000,求n
//此题可以利用break语句在和大于1000时结束循环，输出n的值
public static void deal() {
  int sum = 0;
  int i = 1;
  for (; ; i++) {
   sum = sum + i;
   if (sum > 1000) {
    break;//当和大于1000时，利用break语句跳出循环
   }
  }
  System.out.println(i);
 }

public class LoopTest{
 public static void main(String[] args){
  int bai = 0;
  int shi = 0;
  int ge = 0;
  for(int i = 100; i < 1000; i++){
   bai = i/100;
   shi = i/10%10;
   ge = i%10;
   if(bai*bai*bai+shi*shi*shi+ge*ge*ge == i ){
    System.out.println(i);
   }
  }
 }
}

public class LoopTest{
 public static void main(String[] args){
  char lower = 'a';
  char upper = 'A';
  for(int i = 0 ; i < 26 ; i++){
   System.out.println(lower+" "+upper);
   lower++;
   upper++;
  }
 }
}

public class LoopTest{
 public static void main(String[] args){
  for(int i = 1; i <=9 ; i++){
   for(int j = 1 ; j<=i ; j++){
    System.out.print(j+"*"+i+"="+j*i+" ");
   }
   System.out.println();
  }
 }
}

public class ArrayTest{
 public static void main(String[] args){
  int[] arr1 = {4,6,7,1};
  int[] arr2 = {1,2,3,9,10};
  printArray(arr1);
  printArray(arr2);
 }
 public static void printArray(int[] arr){
  System.out.print("[");
  for(int i = 0 ; i <arr.length ; i++){
   if( i == arr.length-1){
    System.out.println(arr[i]+"]");
   }else{
    System.out.print(arr[i]+",");
   }
  }
 }
}

public class ArrayTest{
 public static void main(String[] args){
  int[] arr = {1,2,3,4,7,8,9};
  reverse(arr);
  printArray(arr);
 }
 public static void reverse(int[] arr){
  for(int min=0,max = arr.length-1; min<max ; min++,max--){
   int temp = arr[min];
   arr[min] = arr[max];
   arr[max] = temp;
  }
 }
  public static void printArray(int[] arr){
  System.out.print("[");
  for(int i = 0 ; i <arr.length ; i++){
   if( i == arr.length-1){
    System.out.println(arr[i]+"]");
   }else{
    System.out.print(arr[i]+",");
   }
  }
 }
}

public class ArrayTest{
 public static void main(String[] args){
  int[] arr = {3,1,5,7,8,9,2};
  selectSort(arr);
  printArray(arr);
 }
 public static void selectSort(int[] arr){
  for(int i = 0; i < arr.length-1; i++){
   for(int j = i+1; j<arr.length; j++){
    if(arr[i]>arr[j]){
     int temp = arr[i];
     arr[i] = arr[j];
     arr[j] = temp;
    }
   }
  }
 }
 public static void printArray(int[] arr){
  System.out.print("[");
  for(int i = 0 ; i <arr.length ; i++){
   if( i == arr.length-1){
    System.out.println(arr[i]+"]");
   }else{
    System.out.print(arr[i]+",");
   }
  }
 }
}

public class ArrayTest{
 public static void main(String[] args){
  int[] arr = {3,1,5,7,8,9,2};
  bubbleSort(arr);
  printArray(arr);
 }
 public static void bubbleSort(int[] arr){
  for(int i = 0; i<arr.length-1 ;i++){
   for(int j = 0; j<arr.length-i-1; j++){
    if(arr[j]>arr[j+1]){
     int temp = arr[j];
     arr[j] = arr[j+1];
     arr[j+1] = temp;
    }
   }
  }
 }
 public static void printArray(int[] arr){
  System.out.print("[");
  for(int i = 0 ; i <arr.length ; i++){
   if( i == arr.length-1){
    System.out.println(arr[i]+"]");
   }else{
    System.out.print(arr[i]+",");
   }
  }
 }
}

public class ArrayTest{
 public static void main(String[] args){
  int[] arr = {1,3,5,7,9,11};
  int index = binarySearch(arr, 7);
  System.out.println(index);
 }
 public static int binarySearch(int[] arr,int key){
  int min = 0;
  int max = arr.length-1;
  int mid = 0;
  while( min<=max ){
   mid = (min+max)/2;
   if(key>arr[mid]){
    min = mid+1;
   }else if(key<arr[mid]){
    max = mid-1;
   }else{
    return mid;
   }
  }
  return -1;
 }
}