String的常见面试题

1 package com.zys.string;
2
3 public class Demo3_StringMianShi {
4
5 /**
6 * &＃64;此中的equals()方法是String中的&＃xff0c;与Object中的equals()方法不一样
7 * 这些是String常见的面试题
8 */
9 public static void main(String[] args) {
10 //demo1();
11 //demo2();
12 //demo3();
13 //demo4();
14 String s1 &＃61; "ab";
15 String s2 &＃61;"abc";
16 String s3 &＃61; s1 &＃43; "c";
17 System.out.println(s3 &＃61;&＃61; s2);//false s1,s2都在常量池中&＃xff0c;s3&＃43;"c"是一个StringBuffer对象&＃xff0c;必须得转换成String对象
18 System.out.println(s3.equals(s2));//true
19 }
20
21 private static void demo4() {
22 String s1 &＃61; "a" &＃43; "b" &＃43; "c";
23 String s2 &＃61; "abc";
24 System.out.println(s1 &＃61;&＃61; s2);//true java中有常量优化机制
25 System.out.println(s1.equals(s2));//true
26 }
27
28 private static void demo3() {
29 String s1 &＃61; new String("abc");
30 String s2 &＃61; "abc";
31 System.out.println(s1 &＃61;&＃61; s2);//false
32 System.out.println(s1.equals(s2));//true
33 }
34
35 private static void demo2() {
36 //下面这段代码共创建了对象
37 String s1 &＃61; new String("abc");//俩个对象,因为它new了中&＃xff0c;在堆内存中开辟了一块空间&＃xff0c;有地址值
38 System.out.println(s1);
39 }
40
41 private static void demo1() {
42 /*
43 * 俩个都为true&＃xff0c;因为s1,s2指向同一对象&＃xff0c;都处于常量变量池
44 */
45 String s1 &＃61; "abc";
46 String s2 &＃61; "abc";
47 System.out.println(s1 &＃61;&＃61; s2);//true
48 System.out.println(s1.equals(s2));//true
49 }
50
51 }