java入门基础学习----数组

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二维数组

int [4][];        //合法

int [][4];         //非法

数组的拷贝       

public static void arraycopy(Object src, int srcPos, Object dest, int destPos, int length)

增强的for循环，相当于foreach遍历数组

int[] d= {1,2,3,4,5,6,2,323,234,45,45};
for(int i:d) {
	System.out.println(i);
}

冒泡排序

package cn.bjsxt.BubbleSort;
/**
 * 测试冒泡排序
 * @author Administrator
 *
 */
public class Bubble {
	public static void main(String[] args) {
		int[] arr = {9,8,7,6,5,4,3,2,1};
		
		for (int i = 0; i < arr.length-1; i++) {
			for (int j = 0; j < arr.length-1-i; j++) {
				if (arr[j]>arr[j+1]) {
					int temp = arr[j];
					arr[j] =arr[j+1];
					arr[j+1]=temp;
				}				
			}
		}
		
		for (int k : arr) {
			System.out.print(k+"\t");
		}
	}
}

二分法查找元素

package cn.bjsxt.Sort;

/**
 * 测试二分法
 * @author Administrator
 *
 */
public class BinarySort {
	public static void main(String[] args) {
		int[] arr = {0,1,2,3,4,5,6,7,8,9,10};
		System.out.println(binary(arr,10));
		
	}
	public static int binary(int[] arr,int targetvalue) {
		int min = 0;
		int max = arr.length-1;
		int mid = arr.length/2;
		if(arr[mid]==targetvalue) {
			return mid;
		}
		while (min<=max) {
			mid = (max-min)/2+min;
			if(targetvalue<arr[mid]) {
				max = mid-1;
			}
			else if(targetvalue>arr[mid]) {
				min = mid+1;
			}
			else {
				return mid;
			}
		}
		return -1;
	}
}