JavaSE基础篇 -- jdk配置，数组及其应用，栈和堆内存图解(Java源码)

/** JavaSE--一维数组应用举例 @author: lichunchun @date: 2015.01.29 */ import java.lang.*; import java.util.*; class ArrayTest{ public static void main(String[] args){ int[] arr = {32,45,2,4,56,78,43,1,3}; int[] arr1 = {54,34,56,7,84,43,5,13}; int[] arr2 = {32,34,54,6,53,71,8,934,57,23}; int[] arr3 = {2,3,5,6,14,23,34,56,88}; System.out.println("------------------------\narr[]:"); printArray(arr); System.out.println("选择排序："); selectSort(arr); printArray(arr); System.out.println("------------------------\narr1[]:"); printArray(arr1); System.out.println("冒泡排序："); bubbleSort(arr1); printArray(arr1); System.out.println("------------------------\n实际开发："); System.out.println("Arrays.sort(arr);"); int sum = add(arr); int max = getMax(arr); System.out.println("------------------------"); System.out.println("sum of arr = "+sum); System.out.println("------------------------"); System.out.println("max of arr = "+max); System.out.println("========================"); System.out.println("arr2[]:"); printArray(arr2); System.out.println("------------------------\narr3[]:"); printArray(arr3); System.out.println("------------------------"); int locate = searchKey(arr2, 8); int locate1 = binarySearch(arr3, 88); System.out.println(8+" in arr2[] is located in "+locate); System.out.println("------------------------"); System.out.println(88+" in arr3[] is located in "+locate1); System.out.println("------------------------\n反转arr3:"); reverse(arr3); printArray(arr3); System.out.println("------------------------\narr4[]:"); int[] arr4 = {2,4,12,32,45,57,67,70}; printArray(arr4); int index = binarySearch_2(arr4, 3); System.out.println("index of inserting 3 to arr4 = "+index); System.out.println("------------------------\n实际开发: "); System.out.println("Arrays.binarySearch(arr, 3);"); System.out.println("========================"); System.out.println("60的进制转换："); int num = 60; String str_bin = toBinary(num); String str_oct = toOctal(num); String str_hex = toHex(num); System.out.println("bin:"+str_bin); System.out.println("oct:"+str_oct); System.out.println("hex:"+str_hex); System.out.println("-------------------------\n实际开发："); System.out.println("bin: Integer.toBinaryString(num)"); System.out.println("oct: Integer.toOctalString(num)"); System.out.println("hex: Integer.toHexString(num)"); System.out.println("-------------------------"); } public static int add(int[] arr){ //数组求和 int sum = 0; for (int x = 0; x < arr.length; x++){ sum += arr[x]; } return sum; } public static int getMax(int[] arr){ //数组求最值(方法一) int max = arr[0]; for (int x = 1; x < arr.length; x++){ if (arr[x] > max){ max = arr[x]; } } return max; } public static int getMax_2(int[] arr){ //数组求最值(方法二) int max = 0; for (int x = 1; x < arr.length; x++){ if (arr[x] > arr[max]){ max = x; } } return arr[max]; } public static void selectSort(int[] arr){ //选择排序 for (int x = 0; x < arr.length-1; x++){ for (int y = x+1; y < arr.length; y++){ if (arr[x] > arr[y]){ swap(arr, x, y); } } } } public static void bubbleSort(int[] arr){ //冒泡排序 for (int x = 0; x < arr.length-1; x++){ for (int y = 0; y < arr.length-1-x; y++){ if (arr[y] > arr[y+1]){ swap(arr, y, y+1); } } } } public static int searchKey(int[] arr, int key){ //遍历查找 for (int x = 0; x < arr.length; x++){ if (arr[x] == key) return x; } return -1;//-1, 代表的是角标不存在的情况。 } public static int binarySearch_1(int[] arr, int key){ //二分查找(方法一) /*二分查找，前提：数组必须是有序的。*/ int min, max, mid; min = 0; max = arr.length-1; mid = (min+max)>>1; while (arr[mid] != key){ if (arr[mid] > key) max = mid-1; else if (arr[mid] < key) min = mid+1; if (min > max) return -1; mid = (min+max)>>1; } return mid; } public static int binarySearch(int[] arr, int key){ //二分查找(方法二) int min, max, mid; min = 0; max = arr.length-1; while (min <= max){ mid = (min+max)>>1; if (arr[mid] > key) max = mid-1; else if (arr[mid] < key) min = mid+1; else return mid; } return -1; } public static void reverse(int[] arr){ //数组反转 for (int start=0, end=arr.length-1; start<end; start++, end--){ swap(arr, start, end); } } public static int binarySearch_2(int[] arr, int key){ //插入位置 int min, max, mid; min = 0; max = arr.length-1; while (min <= max){ mid = (min+max)>>1; if (arr[mid] > key) max = mid-1; else if (arr[mid] < key) min = mid+1; else return mid; } return min;//直接返回插入位置 //return -(1+min);//和Arrays.binarySearch结果一致 } public static void swap(int[] arr, int a, int b){ //交换数组两个元素 /*注意是三个参数，不是两个，否则无法交换*/ int temp = arr[a]; arr[a] = arr[b]; arr[b] = temp; } public static void printArray(int[] arr){ //打印数组 for (int x = 0; x < arr.length; x++){ if (x != arr.length-1) System.out.print(arr[x]+","); else System.out.println(arr[x]); } } public static String toBinary(int num){ return trans(num, 1, 1); } public static String toOctal(int num){ if (num == 0)//后面学到string流时，会说到，比较trans()结果和"0"的关系，进行判断。 return trans(num, 7, 3); else return "0"+trans(num, 7, 3); } public static String toHex(int num){ if (num == 0) return trans(num, 15, 4); else return "0x"+trans(num, 15,4); } public static String trans(int num, int base, int offset){ if (num == 0) return "0"; char[] chs = {'0','1','2','3', '4','5','6','7', '8','9','A','B', 'C','D','E','F'}; char[] arr = new char[32]; int index = arr.length; while (num != 0){ int temp = num & base; arr[--index] = chs[temp]; num = num >>> offset; } return toString(arr, index); } public static String toString(char[] arr, int index){ String temp = ""; for (int x = index; x < arr.length; x++){ temp = temp + arr[x]; } return temp; } }