【java】System成员输入输出功能out、in、err

package System输入输出; import java.io.ByteArrayOutputStream;
import java.io.File;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.OutputStream;
import java.util.function.Consumer; public class Test {
public static void main(String[] args) throws IOException {
/*
try{
int i=3/0;
}catch(Exception e){
e.printStackTrace();
System.out.println(e);//输出信息红色
System.err.println(e);//输出信息黑色
}
*/
//输出到屏幕
OutputStream out=System.out;
//输出到文件
OutputStream out2=new FileOutputStream(new File("D:"+File.separator+"test.txt"));
//输出到内存
OutputStream out3=new ByteArrayOutputStream();
//以上体现多态性
out.write("Welcom to 中国\n".getBytes()); Consumer<String> consumer=System.out::println;
consumer.accept("北京欢迎你！");
}
}

package System输入输出; import java.io.IOException;
import java.io.InputStream; public class Test {
public static void main(String[] args) throws IOException {
InputStream in=System.in;
byte[] b=new byte[1024];
System.out.println("请输入数据：");
int len=in.read(b);
System.out.println(new String(b,0,len));
}
}

package System输入输出; import java.io.IOException;
import java.io.InputStream; public class Test {
public static void main(String[] args) throws IOException {
InputStream in=System.in;
StringBuffer sb=new StringBuffer();
System.out.println("请输入数据：");
int tmp=0;
while((tmp=in.read())!=-1){
if(tmp=='\n')
break;
sb.append((char)tmp);
}
System.out.println(sb);
}
}