常用的控制台输入类是 java.util.Scanner，能从 System.in 读取各种类型数据
import java.util.Scanner;

Scanner sc = new Scanner(System.in);

System.out.print(“请输入一个整数：”);
int num = sc.nextInt();

System.out.print(“请输入一个浮点数：”);
double d = sc.nextDouble();

System.out.print(“请输入一个单词）：”);
String word = sc.next();

System.out.print(“请输入一行文本：”);
String line = sc.nextLine();

循环读取直到文件结束
while (sc.hasNext()) {
String word = sc.next();
System.out.println(word);
}

while (sc.hasNextLine()) {
String line = sc.nextLine();
System.out.println(line);
}
普通输出
System.out.println(“Hello”); 换行
System.out.print(“No newline”); 不换行