Java 8.10

scanner类
Next

import java.util.Scanner;

public class Mine {
	public static void main(String[] args) {
		Scanner scan = new Scanner(System.in);
		System.out.println("next方式接收： ");
		if(scan.hasNext()) {
			String str1 = scan.next();
			System.out.println("输入的数据为：" + str1);
		}
		scan.close();
	}
}

Nextline (读入一行 可读入空格)

import java.util.Scanner;

public class Mine {
	public static void main(String[] args) {
		Scanner scan = new Scanner(System.in);
		System.out.println("nextline 方式接收： ");
		if(scan.hasNextLine()) {
			String str1 = scan.nextLine();
			System.out.println("输入的数据为：" + str1);
		}
		scan.close();
	}
}

同理的 nextdouble 等

import java.util.Scanner;

public class Mine {
	static <T> void pln(T x) {
		System.out.println(x);
	}
	public static void main(String[] args) {
		Scanner scan = new Scanner(System.in);
		pln("Please enter nubers: ");
		double sum = 0.0;
		int cnt = 0;
		while (scan.hasNextDouble()) {
			double x = scan.nextDouble();
			cnt++;
			sum += x;
		}
		pln("The tot sum of " + cnt + " numbers is: " + sum);
		pln("The average value of " + cnt + " numbers is: " + (double)(sum/cnt));
	}
}

try-catch

public class Mine{
	static <T> void pln(T x) {
		System.out.println(x);
	}
	public static void main(String[] args) {
		try {
			int[] a = new int[2];
			pln("3rd value: " + a[3]);
		} catch (ArrayIndexOutOfBoundsException e) {
			pln("Exeception thrown :" + e);
		}
		pln("Out of the block.");
	}
}

throw:

import java.util.Scanner;

public class Mine{
	static <T> void pln(T x) {
		System.out.println(x);
	}
	public static void check_num(int num) {
		if(num < 0) {
			throw new IllegalArgumentException("Number must be postive!");
		}
	}
	public static void main(String[] args) {
		Scanner scan = new Scanner(System.in);
		pln("Please enter a number: ");
		int num = scan.nextInt();
		Mine.check_num(num);
	}
}

try-with-resources 方法 类似python的 with-open 可以结束语句块的时候自动关闭资源

import java.io.*;

public class Mine{
	static <T> void pln(T x) {
		System.out.println(x);
	}
	public static void main(String[] args) {
		int linecnt = 0;
		String line;
		try(BufferedReader br = new BufferedReader(new FileReader("test.txt"))) {
			while ((line = br.readLine()) != null) {
				linecnt++;
				pln("Line " + linecnt + " => " + line);
			}
		} catch (IOException e) {
			pln("IOException in try block =>" +e.getMessage());
		}
	}
}

自定义异常类:
模拟银行账户操作

import java.*;
import java.util.Scanner;

public class Mine{
	static <T> void pln(T x) {
		System.out.println(x);
	}
	public static void main(String[] args) {
		AccountSimulating cAccountSimulating = new AccountSimulating("123124124124");
		Scanner scan = new Scanner(System.in);
		pln("请输入存款金额：");
		double deposit = scan.nextDouble();
		cAccountSimulating.deposit(deposit);
		try {
			pln("\nWithdrawing ￥100...");
			cAccountSimulating.withdraw(100);
			pln("\nWithdrawing ￥600...");
			cAccountSimulating.withdraw(600);
		} catch (AccountException e) {
			pln("Sorry, but you are short ￥" + e.get_amount());
			e.printStackTrace();
		}
	}
}

class AccountSimulating{//模拟银行账户操作
	private double rest_money;
	private String card_id;
	public AccountSimulating(String card_id) {
		this.card_id = card_id;
	}
	public void deposit(double money) {//存
		rest_money += money;
	}
	public void withdraw(double money) throws AccountException {//取
		if(money <= rest_money) {
			rest_money -= money;
		}
		else {
			double delta = money - rest_money;
			throw new AccountException(delta);
		}
	}
	public double get_restmoney() {//返回余额
		return rest_money;
	}
	public String get_cardid() {//返回卡号
		return card_id;
	}
}

class AccountException extends Exception{
	private double amount;
	public AccountException(double amount) {
		this.amount = amount;
	}
	public double get_amount() {
		return amount;
	}
}