package formatinout;
import java.io.FileInputStream;
import java.io.FileNotFoundException;
import java.io.FileReader;
import java.io.FileWriter;
import java.io.IOException;
import java.util.Scanner;
public class ScannerExample {
public static void main(String args[]) throws IOException {
System.out.println("请输入若干个数,每输入一个数用回车确认");
System.out.println("最后输入一个非数字结束输入操作");
Scanner reader = new Scanner(System.in); // 标准输入
double sum = 0;
int m = 0;
while (reader.hasNextDouble()) {
double x = reader.nextDouble();
m = m + 1;
sum = sum + x;
}
System.out.printf("%d个数的和为%f\n", m, sum);
System.out.printf("%d个数的平均值是%f\n", m, sum / m); // 格式化输出
try {
FileInputStream fi = new FileInputStream("c:/a.txt");
FileReader fr = new FileReader("c:/a.txt");
FileWriter fw = new FileWriter("c:/a.txt",true);
fw.write(99); // 写入“c”
fw.append('x'); //写入"x"
fw.close(); //必须有,否则写不进去
byte[] buffer = new byte[20]; // zi jie liu
char[]charbuff = new char[20]; //zi fu liu
try {
int readchar = fr.read(charbuff); //zi fu number
System.out.println(readchar); // h
for(int i=0;i<readchar;i++)
System.out.println(charbuff[i]); // h
// e.....
fr.close();
} catch (IOException e1) {
e1.printStackTrace();
}
try {
fi.read(buffer);
String str = new String(buffer);
System.out.println(str); //helloworld
for(int i =0;i<buffer.length;i++)
System.out.println(buffer[i]); //unicode104
// 101
// 108
// 108
// 111
// 119
// 111
// 114
// 108
// 100
fi.close();
} catch (IOException e) {
e.printStackTrace();
}
} catch (FileNotFoundException e) {
e.printStackTrace();
}
}
}
一下是一个对象克隆的例子
实体student
package cloneObject;
public class Student [color=red]implements Cloneable [/color]{
public String id;
public String name;
public Object clone() {
Student o = null;
try {
o = (Student) super.clone();
} catch (Exception e) {
throw new java.lang.IllegalStateException("Clone 出错!"
+ e.toString());
}
return o;
}
}
测试类Test
package cloneObject;
public class TestClone {
public static void main(String[] args) {
Student stu1 = new Student();
stu1.id="1";
stu1.name = "stu1";
Student stu2 = (Student) stu1.clone();
//对象复制,如果直接用stu2 = stu1;引用的是同一个对象,改变任何一个将对另一个造成影响
System.out.println(stu2.id+stu2.name);
stu2.id ="2";
System.out.println(stu2.id+stu2.name);
System.out.println(stu1.id+stu2.name);
}
}
结果
1stu1
2stu1
1stu1
源码见附件:
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