【Java_SE】作业练习1104

1.需求：请设计一个方法，可以实现获取任意范围内的随机数

import java.util.Random;import java.util.Scanner;public class Demo1 {    public static void main(String[] args) {        Scanner sc=new Scanner(System.in);        System.out.println("请设置上限：");        int start=sc.nextInt();        System.out.println("请设置下限：");        int end=sc.nextInt();        int result=getRandom(start,end);        System.out.println(result);    }    //产生随机数方法    public static int getRandom(int start,int end){        Random r=new Random();        int random=0;        //如果不在设定的上下限中，则继续产生随机数        while(!(random>=start)){            random=r.nextInt(end);        }        return random;    }}

2.下面代码执行的结果是:

public static void main(String[] args) {        String s1 = new String("hello");        String s2 = new String("hello");        System.out.print(s1 == s2);//结果：false        System.out.print(",");        System.out.println(s1.equals(s2));//结果：true    }}

3.下面代码执行的结果是:

public static void main(String arg[]) {        StringBuffer a = new StringBuffer("A");        StringBuffer b = new StringBuffer("B");        operate(a, b);        System.out.println(a + "," + b);//结果:AB,B    }    static void operate(StringBuffer x, StringBuffer y) {        x.append(y);        y = x;    }}

4.下列代码的执行结果是：

public static void main(String [] args){    String str1 = "This is a test!";    StringBuffer str2 =new StringBuffer( "This is a test!");    str1 = str1+"Hi";    str2.append("Hi");    System.out.println("str1 == " + str1);//结果：str1 == This is a test!Hi    System.out.println("str2 == " + str2);//结果：str2 == This is a test!Hi}

5:下面代码能最后打印的值是?　　　答案：C）0

public class TestValue {    private static int a;    public static void main(String[] args) {        modify(a);        System.out.println(a);    }    public static void modify(int a) {        a++;    }}

A）编译错误　　B）null　　C）0　　D）1