1.输出100到1000的水仙花数：
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);
}
}
}
}
2.打印所有字母：
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++;
}
}
}
3.打印99乘法表：
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();
}
}
}
4.按格式遍历数组：
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]+",");
}
}
}
}
5.数组元素逆序（注意：不是反向遍历）：
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]+",");
}
}
}
}
6.选择排序：
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]+",");
}
}
}
}
7.冒泡排序：
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]+",");
}
}
}
}
8.折半查找法（注意必须是有序的数组）：
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;
}
}