Java输入IP，判断IP是否正确

傷城~ 2021-11-10 07:20 437阅读 0赞

Java输入IP，判断IP是否正确

方法一：字符判断

import java.util.Scanner;
    
    /*
     * 输入ip，判断ip是否正确
     */
    public class IPJudge {
    
    	public static void main(String[] args) {
    		System.out.println("请输入ip地址：");
    		Scanner sc = new Scanner(System.in);
    		String strIP = sc.nextLine();
    		// 判断是否数字和点构成
    		boolean canJudge = numberPoint(strIP);
    		// 判断有几个点
    		int pointCounts = pointCounts(strIP, canJudge);
    		// 判断数字部分是否0-255
    		numberJduge(strIP, pointCounts);
    		sc.close();
    	}
    
    	private static void numberJduge(String strIP, int pointCounts) {
    		boolean isTrue = true;
    		int tempNumber[] = new int[4];
    		if (pointCounts == 3) {
    			String temp[] = strIP.split("\\.");
    			for (int i = 0; i < tempNumber.length; i++) {
    				tempNumber[i] = Integer.parseInt(temp[i]);
    			}
    			for (int j = 0; j < tempNumber.length; j++) {
    				if (255 < tempNumber[j] || tempNumber[j] < 0) {
    					isTrue = false;
    					break;
    				}
    			}
    			if (isTrue) {
    				System.out.println("IP格式正确：" + strIP);
    			} else {
    				System.out.println("IP格式错误！");
    			}
    		} else {
    			System.out.println("IP格式错误！");
    		}
    	}
    
    	private static int pointCounts(String strIP, boolean canJudge) {
    		int pointCounts = 0;
    		if (canJudge) {
    			for (int i = 0; i < strIP.length(); i++) {
    				if (strIP.charAt(i) == '.') {
    					pointCounts++;
    				}
    			}
    		}
    		return pointCounts;
    	}
    
    	private static boolean numberPoint(String strIP) {
    
    		boolean canJudge = true;
    		for (int i = 0; i < strIP.length(); i++) {
    			if (strIP.charAt(0) == '.' || strIP.charAt(strIP.length() - 1) == '.') {
    				canJudge = false;
    				break;
    			} else if (57 < strIP.charAt(i) || strIP.charAt(i) < 48 && strIP.charAt(i) != '.') {
    				canJudge = false;
    				break;
    			}
    		}
    		return canJudge;
    	}
    
    }

方法二：正则表达式

import java.util.Scanner;
    import java.util.regex.Matcher;
    import java.util.regex.Pattern;
    
    public class IPJudge2 {
    
    	public static void main(String args[]) {
    		System.out.println("请输入ip地址：");
    		Scanner sc = new Scanner(System.in);
    		String strIP = sc.nextLine();
    		String pattern = "((2(5[0-5]|[0-4]\\d))|[0-1]?\\d{1,2})(\\.((2(5[0-5]|[0-4]\\d))|[0-1]?\\d{1,2})){3}";
    		Pattern r = Pattern.compile(pattern);
    		Matcher m = r.matcher(strIP);
    		if (m.matches()) {
    			System.out.println("IP格式正确：" + strIP);
    		} else {
    			System.out.println("IP格式错误！");
    		}
    		sc.close();
    	}
    
    }