笔试题

 1 // 1.判断定义为String类型的s1和s2是否相等
 2      String s1 = "abc";
 3      String s2 = "abc";
 4      System.out.println(s1 == s2);         //true
 5      System.out.println(s1.equals(s2));    //true

 6 // 2.下面这句话在内存中创建了几个对象?
 7     String s1 = new String("abc");        //两个对象

 8 // 3.判断定义为String类型的s1和s2是否相等
 9      String s1 = new String("abc");
10      String s2 = "abc";
11      System.out.println(s1 == s2);          //false
12      System.out.println(s1.equals(s2));     //true  

13 //4.判断定义为String类型的s1和s2是否相等
14      String s1 = "a" + "b" + "c";
15      String s2 = "abc";
16      System.out.println(s1 == s2);          //true 
17      System.out.println(s1.equals(s2));      //true 

18 //5.判断定义为String类型的s1和s2是否相等
19       String s1 = "ab";
20      String s2 = "abc";
21     String s3 = s1 + "c";
22     System.out.println(s3 == s2);          //false      
23     System.out.println(s3.equals(s2));    //true 

 1   public static void main(String[] args) {
 2     String s="amzsvfjdskgn12432549032   ()*&^%";
 3             int kongGe=0;
 4             int ziFu=0;
 5             int other=0;
 6             int num=0;
 7         for (int i = 0; i < s.length(); i++) {
 8             char c=s.charAt(i);
 9             if ((c>=‘a‘&&c<=‘z‘)|(c>=‘A‘&&c<+‘Z‘)){
10                 ziFu++;
11             }else if (c==‘ ‘){
12                 kongGe++;
13             }else if (c>=‘0‘&&c<=‘9‘){
14                 num++;
15             }else {
16                 other++;
17             }
18         }
19         System.out.println(ziFu);
20         System.out.println(kongGe);
21         System.out.println(num);
22         System.out.println(other);
23     }

 1  public static void main(String[] args) {
 2         String max = "wortartiheha,heyeytritrymrtyabutonytyrtrgyubatryia,wultryurytnhetryimytryatyryhaishtryibaa,zhhsaodaogtyurongzughfgojiustryrthihotrytrma";
 3         String min = "heha";
 4         int count = 0;
 5         //定义索引
 6         int index = 0;
 7         //定义循环,判断小串是否在大串中出现
 8         while((index = max.indexOf(min)) != -1) {
 9             count++;
10             max = max.substring(index + min.length());
11         }
12         System.out.println(count);
13         }

public static void main(String[] args) {
        String s = "98 37 86 978 90";
        //1,将字符串切割成字符串数组
        String[] sArr = s.split(" ");
        //2,将字符串转换成数字并将其存储在一个等长度的int数组中
        int[] arr = new int[sArr.length];
        for (int i = 0; i < arr.length; i++) {
            arr[i] = Integer.parseInt(sArr[i]);     //将数字字符串转换成数字
        }
        
        //3,排序
        Arrays.sort(arr);
}

 1     */
 2     public static void main(String[] args) {
 3         ArrayList list = new ArrayList();
 4         list.add("a");
 5         list.add("a");
 6         list.add("b");
 7         list.add("b");
 8         list.add("c");
 9         list.add("c");
10         list.add("c");
11         list.add("c");
12         
13         ArrayList newList = getSingle(list);
14         System.out.println(newList);
15     }
16 
17     /*
18      * 创建新集合将重复元素去掉
19      * 1,明确返回值类型,返回ArrayList
20      * 2,明确参数列表ArrayList
21      *
22      * 分析:
23      * 1,创建新集合
24      * 2,根据传入的集合(老集合)获取迭代器
25      * 3,遍历老集合
26      * 4,通过新集合判断是否包含老集合中的元素,如果包含就不添加,如果不包含就添加
27      */
28     public static ArrayList getSingle(ArrayList list) {
29         ArrayList newList = new ArrayList<>();                    //1,创建新集合
30         Iterator it = list.iterator();                            //2,根据传入的集合(老集合)获取迭代器
31         
32         while(it.hasNext()) {                                    //3,遍历老集合
33             Object obj = it.next();                                //记录住每一个元素
34             if(!newList.contains(obj)) {                        //如果新集合中不包含老集合中的元素
35                 newList.add(obj);                                //将该元素添加
36             }
37         }
38         
39         return newList;
40     }