java语言基础类

public class Dog { String name;
int weight;
public Dog(String name, int weight) {
    this.name = name;
    this.weight = weight; }
public String toString()
{
return this.name + "重" + this.weight + "公斤";
}

public boolean equals(Object obj) {
    if(this == obj) {
        return true;
    }
    if(obj instanceof Dog) {
        Dog dog = (Dog)obj;
        if(dog.weight==this.weight&&dog.name.equals(this.name)) {
            return true; }
    }
    return false; }
public int hashCode() {
int h;
int a=name.hashCode();
h = weight+a;

        return h;

}public static void main(String[] args) {    Dog dog1 = new Dog("DaHuan", 10);    Dog dog2 = new Dog("DaHuan", 10);    System.out.println(dog1);    System.out.println(dog1.equals(dog2));    System.out.println(dog1 == dog2); //地址} }

public class TestMath {
    public static void main(String[] args) {
        double  a = Math.random() * 10; //double->会有损失
        System.out.println("a=" + a);
        System.out.println(a + "的平方根是:" + Math.sqrt(a)); 
    }
}

public class TestString {
    public static void main(String[] args) {
        String name = "My name is chen wei fang";
        System.out.println("字符串的长度是:" + name.length());
        System.out.println("字符串中的第一个字符是:" + name.charAt(0));
        System.out.println("字符串中的最后一个字符是:" + name.charAt(name.length()-1));
        System.out.println("字符串中的第一个单词是:" + name.substring(0,name.indexOf("y")+1));
        System.out.println("字符串中的第一个单词是:" + name.substring(20,name.lastIndexOf("g")+1));
        String s1 = new String("you are a student");
        String s2 = new String("how are you");
        if (s1.equals(s2)) {System.out.println("s1 与 s2 相同"); } else
            {
        System.out.println("s1 与 s2 不相同"); }
if(s1.startsWith("you")){
          System.out.println("s1 是以 you 开头的"); }
if (s2.contains("you")) {
System.out.println("s2 中包含 you");
        }
        String path = "c:/java/A.java";
        int index = path.indexOf("/");
         System.out.println("c:/java/A.java 中第一个/出现的位置是:" + index);
        int lastIndex = path.lastIndexOf("/");
         System.out.println("c:/java/A.java 中最后一个/出现的位置是:" + lastIndex);
        String fileName = path.substring(lastIndex+1,path.length());
       System.out.println("c:ava/A.java 中包含的文件名是:" + fileName);
        }
}

public class TestStringBuffer {
    public static void main(String[] args) {
        String s = "MicroSoft";
        StringBuffer sb = new StringBuffer(s);
        System.out.println(sb.append("Oracle"));
         System.out.println(sb.insert(8,"/"));
        System.out.println(sb.replace(0,8,"MicroSun"));
        System.out.println(sb.delete(0,5));
    } }

import java.util.Random; 
import java.util.Scanner;
public class TestRandom {
    public static void main(String[] args) {
        Scanner scanner = new Scanner(System.in) ;
         Random random = new Random();
        int n = 0;
        System.out.println("输入 0 表示退出循环");
        while(true) {
            System.out.print("请输入 n 的值:");
            n = scanner.nextInt();
             if(n==0) {
            break; }
        System.out.print("生成的[0," + n + "]之间的随机数是:");
        System.out.println(random.nextInt(n+1));
             }
        System.out.println("程序执行结束");
 scanner.close();
    }}

import sun.util.resources.CalendarData;

import java.util.Calendar;

public class TestCalendar {
    public static void main(String[] args) {
        Calendar calendar = Calendar.getInstance();
       calendar.set(Calendar.DATE,1);
        int dayOfWeek =calendar.get(Calendar.DAY_OF_WEEK)-1;
        int maxDate = calendar.getMaximum(Calendar.DATE);
         System.out.println("日\t 一\t 二\t 三\t 四\t 五\t 六");
        for(int i=Calendar.SUNDAY; i<dayOfWeek; i++) {
            System.out.print("\t");
        }
        for(int i=1;i<=maxDate;i++) {
            System.out.print(i + "\t");
            if( (dayOfWeek+i-1)%7==0 ) {
                System.out.println(); }
        } }
}

public class TestException1 {
    static void m() throws Exception{
        int a = 3;
        int b = 0;
        int c = a/b;
        System.out.println(c);
    }
    public static void main(String[] args) {
        try {
            m();
        } catch (Exception e) {
            System.out.println("Wrong");
        } finally
        {
            System.out.println("总会执行");
        }
        System.out.println("程序正常结束");
    }
}

import java.io.BufferedReader;
import java.io.InputStreamReader;
import java.io.IOException;
public class TestException2 {
    public static void main(String[] args)throws IOException{
        BufferedReader br = new BufferedReader( new InputStreamReader(System.in));
        try{
        int x = Integer.parseInt(br.readLine());
        int y = Integer.parseInt(br.readLine());
        System.out.println(x/y);
        br.close();
        }
        catch(Exception e){
            e.printStackTrace();;
        }
        finally {
            br.close();
        }
    } }

异常机制还是不太懂需要看书和多多实践

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java语言基础类

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