java-Array数组常用操作例子（基础必备）

package com.net.xinfang.reflect;

import java.util.ArrayList;
import java.util.Arrays;
import java.util.HashSet;
import java.util.List;
import java.util.Scanner;
import java.util.Set;

import org.apache.commons.lang.ArrayUtils;

public class array001 {
	/***
	 * 数组对象学习
	 */
	public void StrArray() {
		String[] str = new String[] { "我", "是", "数组" };
		// String[] str={ "我", "是", "数组" };
		System.out.println(str.length);// 输出数组长度
		boolean b = Arrays.asList(str).contains("我");// 转换为list再判断是否包含
		if (b) {
			System.out.println("exist");
		}
		// for遍历输出数组
		for (int i = 0; i < str.length; i++) {
			System.out.println(str[i]);
		}
		// foreach遍历输出数组
		for (String j : str) {
			System.out.println(j);
		}
		int arr[][] = new int[][] { { 1 }, { 2, 3 }, { 4, 5, 6 } }; // 二维数组
		// for循环遍历二维数组。
		for (int i = 0; i < arr.length; i++) {
			for (int j = 0; j < arr[i].length; j++) {
				System.out.print(arr[i][j]);
			}
			System.out.println();
		}
		// foreach语句遍历二维数组。
		for (int x[] : arr) { // 外层遍历得到一维数组
			for (int e : x) { // 内层遍历得到数组元素
				System.out.print(e);
			}
			System.out.println();
		}
		// 连接两个数组
		int[] arr1 = { 1, 2 };
		int[] arr2 = { 3 };
		int[] combArr = ArrayUtils.addAll(arr1, arr2);
		for (int k : combArr) {
			System.out.println(k);
		}
		// 数组逆向输出
		int[] arra = { 1, 2, 3 };
		ArrayUtils.reverse(arra);
		System.out.println(Arrays.toString(arra));
		// int数组转换为String
		int[] array3 = { 9, 0 };
		String arrStrings = Arrays.toString(array3);
		System.out.println(arrStrings);
		// 将数组转换ArrayList动态数组
		ArrayList<String> arrayList = new ArrayList<String>(Arrays.asList(str));
		Set<String> set = new HashSet<String>(Arrays.asList(str));// 转换为set集合
		System.out.println(set);
		System.out.println(arrayList);
		// 将数组转换为数组
		String[] array2 = new String[] { "黄渤", "张艺兴", "孙红雷" };
		// 方法 1.
		List<String> list = new ArrayList<String>();
		for (int i = 0; i < array2.length; i++) {
			list.add(array2[i]);
		}
		System.out.println(list);
		String[] arrStrings2 = { "1", "2", "3" };
		// 方法 2.
		List<String> list2 = java.util.Arrays.asList(arrStrings2);
		System.out.println(list2);
		// 填充数组
		int[] arr3 = new int[2];
		Arrays.fill(arr3, 10); // 将数组全部填充10
		// 遍历输出
		for (int i = 0; i < arr3.length; i++) {
			System.out.println(arr3[i]);
		}
		// 数组排序
		int[] arr4 = { 3, 7 };
		Arrays.sort(arr4);
		for (int i = 0; i < arr4.length; i++) {
			System.out.println(arr4[i]);
		}
		// 比较两个数组
		int[] arr9 = { 1, 2, 3, 4, 5, 6, 7, 8, 9, 0 };
		boolean arr10 = Arrays.equals(arr4, arr9);
		System.out.println(arr10);
		// 数组去重
		int[] arr11 = { 1, 2, 3, 4, 5, 6, 7, 8, 9, 0, 3, 2, 4, 5, 6, 7, 4, 32, 2, 1, 1, 4, 6, 3 };
		// 利用set的特性
		Set<Integer> set2 = new HashSet<Integer>();
		for (int i = 0; i < arr11.length; i++) {
			set2.add(arr11[i]);
		}
		System.out.println(set2);
		int[] arr12 = new int[set2.size()];
		int j = 0;
		for (Integer i : set2) {
			arr12[j++] = i;
		}
		System.out.println(Arrays.toString(arr12));
		// 求数组的最大值和最小值
		int max = arr11[0];
		for (int i = 1; i < arr11.length; i++) {
			if (arr11[i] > max) {
				max = arr11[i];
			}
		}
		System.out.println("Max is " + max);
		// 计算最小值
		int min = arr11[0];
		for (int i = 0; i < arr11.length; i++) {
			if (arr11[i] < min) {
				min = arr11[i];
			}
		}
		System.out.println("Min is " + min);
	}

	// 递归函数字符串反转
	public String reverse(String str) {
		if ((null == str) || (str.length() <= 1)) {
			return str;
		}
		return new StringBuilder(str).reverse().toString();
	}

	// 倒序输出
	public void reversa(String str) {
		for (int i = str.length() - 1; i >= 0; i--) {
			char c = str.charAt(i);
			System.out.println(c);
		}
	}

	public String reverse3(String s) {
		char[] array = s.toCharArray(); // 将string类型参数转化为char[]类型参数
		String reverse = ""; // 注意这是空串，不是null
		for (int i = array.length - 1; i >= 0; i--)
			reverse += array[i];
		return reverse;
	}

	public String reverse2(String s) {
		int length = s.length();
		String reverse = "";
		for (int i = 0; i < length; i++)
			reverse = s.charAt(i) + reverse;// 字符串拼接先来排后面
		return reverse;
	}

	// 字符转换为数组，二分法
	public void reversb(String str) {
		char[] strArray = str.toCharArray();// 将字符串转换为数组
		int len = strArray.length;
		char temp;
		for (int i = 0; i < len / 2; i++) { // 从中间向两边对换
			temp = strArray[i];
			strArray[i] = strArray[len - i - 1];
			strArray[len - i - 1] = temp;
		}
		String strAfter = String.valueOf(strArray);// 数组转换为字符串
		System.out.println(strAfter);
	}

	// 选择排序（选择第一个与第二个比较，大的排后面,依次类推）
	public void SelectSort(int[] a) {
		for (int i = 0; i < a.length - 1; i++) {
			for (int j = i + 1; j < a.length; j++) {
				if (a[i] > a[j]) {
					// 交换两个值
					int temp = a[j];
					a[j] = a[i];
					a[i] = temp;
				}
			}
		}
		for (int k : a) {
			System.out.print(k);
		}
	}

	// 冒泡排序（第1个与第2个比较 ）
	public void bubblSort(int a[]) {
		for (int i = 0; i < a.length - 1; i++) {
			for (int j = 0; j < a.length - 1 - i; j++) {
				if (a[j] > a[j + 1]) {
					int temp = a[j + 1];
					a[j + 1] = a[j];
					a[j] = temp;
				}
			}
		}
		for (int k : a) {
			System.out.print(k);
		}
	}

	// 遍历判断查找
	public int oneByoneSearch(int[] a, int value) {
		for (int i = 0; i < a.length; i++) {
			if (a[i] == value) {
				return i;
			}
		}
		return -1;
	}

	// 二分查找
	public int halfSearch2(int[] a, int value) {
		int left = 0;
		int right = a.length - 1;
		int mid;
		while (left <= right) {
			mid = (left + right) >> 1;
			if (a[mid] == value) {
				return mid;
			} else if (a[mid] > value) {
				right = mid - 1;
			} else {
				left = mid + 1;
			}
		}
		return -1;
	}

	public static void main(String args[]) {
		array001 ay = new array001();
		ay.StrArray();
		String a = "abc";
		System.out.println(ay.reverse(a));
		ay.reversa(a);
		ay.reversb(a);
		ay.reverse3(a);
		int b[] = { 1, 3, 5, 6 };
		ay.SelectSort(b);
		ay.halfSearch2(b, 3);
		ay.bubblSort(b);
		ay.oneByoneSearch(b, 5);
		// 最简单的方法实现字符串反转
		@SuppressWarnings("resource")
		Scanner in = new Scanner(System.in);
		while (in.hasNext()) {
			String line = in.nextLine();// next()是遇到空格；nextLine()是遇到回车
			StringBuffer sb = new StringBuffer(line);
			sb.reverse();
			System.out.println(sb.toString());
		}
	}

}