11.4java作业
2017-11-09 23:35
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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。
public class Test {
public static void main(String[] args) {
for(int i = 0; i<100; i++) {
System.out.println(getRandom());
}
}
private static int getRandom() {
int number = (int)(Math.random()*100)+1;
return number;
}
}
2:下面代码执行的结果是:false,true
public static void main(String[] args) {
String s1 = new String("hello");
String s2 = new String("hello");
System.out.print(s1 == s2);//false
System.out.print(",");
System.out.println(s1.equals(s2));//true
}
}
3:下面代码执行的结果是:AB,B
public static void main(String arg[]) {
StringBuffer a = new StringBuffer("A");
StringBuffer b = new StringBuffer("B");
operate(a, b);
System.out.println(a + "," + b);//AB,B
}
static void operate(StringBuffer x, StringBuffer y) {
x.append(y);
y = x;
}
4:下面代码执行的结果是
6、下列代码的执行结果是:str1 == This is a test!Hi
str2 == This is a test!Hi
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);//str1 == This is a test!Hi
System.out.println("str2 == " + str2);//str2 == This is a test!Hi
7:下面代码能最后打印的值是?C
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 //C
2:获取10个1-20之间的随机数,要求不能重复
package Random;
import java.util.ArrayList;
import java.util.Collection;
import java.util.Random;
public class RandomDemo {
public static void main(String[] args) {
//创建产生随机数的对象
Random r = new Random();
//创建一个存储随机数的集合
Collection array = new ArrayList();
//定义一个计数器
int count = 0;
//判断计数器是否小于10
while(count<10) {
//产生一个随机数
int number = r.nextInt(20)+1;
//判断该随机数在集合中是否存在
if(!array.contains(number)) {
//如果不存在,就添加,统计变量++
array.add(number);
count++;
}
}
//遍历集合
for(int x = 0 ; x<array.size();x++) {
System.out.println(array);
}
}
}
3:使用ArrayList集合存储自定义对象并遍历(三种方式去实现)
package Collection;
import java.util.ArrayList;
import java.util.Iterator;
class Person{
String name;
int age;
Person(String name,int age)
{
this.name=name;
this.age=age;
}
}
public class ArrayListTest1 {
public static void main(String[] args) {
ArrayList a = new ArrayList();
a.add(new Person("张三",28));
a.add(new Person("李四",26));
Iterator i = a.iterator();
while(i.hasNext()) {
Person f = (Person)i.next();
System.out.println(f.name+" "+f.age);
}
}
}
public class Test {
public static void main(String[] args) {
for(int i = 0; i<100; i++) {
System.out.println(getRandom());
}
}
private static int getRandom() {
int number = (int)(Math.random()*100)+1;
return number;
}
}
2:下面代码执行的结果是:false,true
public static void main(String[] args) {
String s1 = new String("hello");
String s2 = new String("hello");
System.out.print(s1 == s2);//false
System.out.print(",");
System.out.println(s1.equals(s2));//true
}
}
3:下面代码执行的结果是:AB,B
public static void main(String arg[]) {
StringBuffer a = new StringBuffer("A");
StringBuffer b = new StringBuffer("B");
operate(a, b);
System.out.println(a + "," + b);//AB,B
}
static void operate(StringBuffer x, StringBuffer y) {
x.append(y);
y = x;
}
4:下面代码执行的结果是
6、下列代码的执行结果是:str1 == This is a test!Hi
str2 == This is a test!Hi
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);//str1 == This is a test!Hi
System.out.println("str2 == " + str2);//str2 == This is a test!Hi
7:下面代码能最后打印的值是?C
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 //C
2:获取10个1-20之间的随机数,要求不能重复
package Random;
import java.util.ArrayList;
import java.util.Collection;
import java.util.Random;
public class RandomDemo {
public static void main(String[] args) {
//创建产生随机数的对象
Random r = new Random();
//创建一个存储随机数的集合
Collection array = new ArrayList();
//定义一个计数器
int count = 0;
//判断计数器是否小于10
while(count<10) {
//产生一个随机数
int number = r.nextInt(20)+1;
//判断该随机数在集合中是否存在
if(!array.contains(number)) {
//如果不存在,就添加,统计变量++
array.add(number);
count++;
}
}
//遍历集合
for(int x = 0 ; x<array.size();x++) {
System.out.println(array);
}
}
}
3:使用ArrayList集合存储自定义对象并遍历(三种方式去实现)
package Collection;
import java.util.ArrayList;
import java.util.Iterator;
class Person{
String name;
int age;
Person(String name,int age)
{
this.name=name;
this.age=age;
}
}
public class ArrayListTest1 {
public static void main(String[] args) {
ArrayList a = new ArrayList();
a.add(new Person("张三",28));
a.add(new Person("李四",26));
Iterator i = a.iterator();
while(i.hasNext()) {
Person f = (Person)i.next();
System.out.println(f.name+" "+f.age);
}
}
}
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