常见java笔试-编程题

1-以指定编码，输出字符串

<span style="font-size:18px;"><span style="font-size:18px;"><span style="font-size:18px;"><span style="font-size:14px;">public class Bianma {public static void main(String[] args) throws UnsupportedEncodingException {String str = "你好aABC";String str2 = new String(str.getBytes("gbk"));System.out.println(str2);}}</span></span></span></span>

2-冒泡排序

<span style="font-size:18px;"><span style="font-size:18px;"><span style="font-size:18px;"><span style="font-size:14px;">package maopao;import java.util.Arrays;public class MaoPao {/** * 冒泡排序算法的运作如下:     比较相邻的元素。如果第一个比第二个大，就交换他们两个。     对每一对相邻元素作同样的工作，从开始第一对到结尾的最后一对。在这一点，最后的元素应该会是最大的数。     针对所有的元素重复以上的步骤，除了最后一个。     持续每次对越来越少的元素重复上面的步骤，直到没有任何一对数字需要比较。 * @param args */public static void main(String[] args) {int[] arr = new int[]{77,10,5,55,58,0,122,45,7,-1,66,65};for(int i=0;i<arr.length;i++){for(int j=0;j<arr.length-i-1;j++){if(arr[j]>arr[j+1]){int a = arr[j+1];arr[j+1] = arr[j];arr[j] = a;}}}System.out.println(Arrays.toString(arr));}}</span></span></span></span>

3-求一个数的阶乘

<span style="font-size:18px;"><span style="font-size:18px;"><span style="font-size:18px;"><span style="font-size:14px;">package jiechengg;public class JieCheng {public static void main(String[] args) {System.out.println(JieCheng(2));}public static int JieCheng(int a) {int count = 1;for (int i = a; a >= 1; a--) {count = a * count;}return count;}}</span></span></span></span>

4-给定一个字符串（全是字母），按升序排序

<span style="font-size:18px;"><span style="font-size:18px;"><span style="font-size:18px;"><span style="font-size:14px;">import java.util.Arrays;public class StringTest {public static void main(String[] args) {String str = "sdheasbvzdx";String[] s = str.split("");Arrays.sort(s);for (int i = 0; i < s.length; i++) {System.out.print(s[i]);}}}</span></span></span></span>

5-给定一个字符串（全是数字），按升序排序

<span style="font-size:18px;"><span style="font-size:18px;"><span style="font-size:18px;"><span style="font-size:14px;">import java.util.Arrays;public class StringTest {public static void main(String[] args) {String str = "1101246987";String[] s = str.split("");Arrays.sort(s);for (int i = 0; i < s.length; i++) {System.out.print(s[i]);}}}</span></span></span></span>

或

<span style="font-size:18px;"><span style="font-size:18px;"><span style="font-size:18px;"><span style="font-size:14px;">import java.util.Arrays;public class StringTest {public static void main(String[] args) {String str = "1101246987";//String[] s = str.split("");//Arrays.sort(s);//for (int i = 0; i < s.length; i++) {//System.out.print(s[i]);//}char[] ch = str.toCharArray();for(int i=0;i<ch.length;i++){for(int j=0;j<ch.length-i-1;j++){if(ch[j]>ch[j+1]){char a = ch[j];ch[j] = ch[j+1];ch[j+1] = a;}}}System.out.println(Arrays.toString(ch));}}</span></span></span></span>

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6-给定一个整型数组，求出其中只出现过一次的数

<span style="font-size:18px;"><span style="font-size:18px;"><span style="font-size:18px;">public class OnlyOneForTwo {public static void main(String[] args) {int[] arr = new int[]{3,5,6,7,8,3,5,6,7,8,9,0};for(int i=0;i<arr.length;i++){int num = 0;for(int j=0;j<arr.length;j++){if(arr[i]==arr[j]){num++;}}if(num==1){System.out.println("这个数出现了一次:"+arr[i]);}}}}</span></span></span>

7-请写一个单例

<span style="font-size:18px;"><span style="font-size:18px;">public class Single {//把单例对象声明为静态，始终保持在内存中只有一份private static Single single = null;//私有构造器方法 使得外部不可以通过传统的new来实例化这个对象//注：不可以省略，省略了，就是public修饰的构造器了private Single(){}//为了线程安全 使用 synchronized 方法锁 public static synchronized Single getInstance(){//如果对象不存在，就创建对象if(single==null){single = new Single();}//否则，就返回已经存在的实例return single;}}</span></span>

8-字符串变量，结果题

<span style="font-size:18px;">public class StringTest2 {public static void main(String[] args) {String abc = "haha";abc = "123";System.out.println(abc);}}</span>

输出结果-123

9-子父类继承关系题

<span style="font-size:18px;">package extendsTest;public class Father {private String name = "小头爸爸";private int age = 40;public void say(){System.out.println("I'm Father...");}public String getName() {return name;}public void setName(String name) {this.name = name;}public int getAge() {return age;}public void setAge(int age) {this.age = age;}}package extendsTest;class Child extends Father{private String name = "大头儿子";private int age = 17;public void say(){System.out.println("I'm Child...");}public String getName() {return name;}public void setName(String name) {this.name = name;}public int getAge() {return age;}public void setAge(int age) {this.age = age;}}package extendsTest;public class TestExtends {public static void main(String[] args) {Father f = new Father();f.say();System.out.println(f.getName());System.out.println("==================");Father f2 = new Child();f2.say();System.out.println(f2.getName());System.out.println("==================");Child c = new Child();c.say();System.out.println(c.getName());}}</span>

输出结果-

I'm Father...

小头爸爸

==================

I'm Child...

大头儿子

==================

I'm Child...

大头儿子