【筆記】Java

public class Main {
    public static void main(String[] args) {
        ...
    }
}

import java.util.Scanner;

Scanner scanner = new Scanner(System.in);
int n = scanner.nextInt();

System.out.println("Hello World"); //換行
System.out.print("Hello World"); //不換行

String s = "Andy";
System.out.println(s.equals("Sandy"));

String s1 = "Hello ";
String s2 = "World";
System.out.println(s1.concat(s2)); //Hello World

int[] arr = {1, 2, 3, 4, 5};
int[] arr = new int[5];

import java.util.ArrayList;

ArrayList<Integer> arr = new ArrayList<Integer>();

arr.add(10);
arr.add(20);
arr.add(30);

arr.set(2, 87); //set index 2 to 87

arr.remove(0); //remove index 0
arr.remove(Integer.valueOf(20));

System.out.println(arr); //87

int[][] arr = {{1,2,3},{4,5,6},{7,8,9}};

for(int i=0; i<3; i++){
    for(int j=0; j<3; j++){
        System.out.print(arr[i][j] + " ");
    }
    System.out.println();
}

try {
    //檢查此區塊程式是否有例外
} catch (例外類型 ex) {
    //處理例外
} finally {
    //可有可無，無論是否有例外都會執行
}

try {
    System.out.println(5 / 0);
} catch (ArithmeticException ex) {
    System.out.println(ex.getMessage()); // / by zero
}

try {
    int[] arr = new int[5];
    arr[5] = 2;
} catch (ArrayIndexOutOfBoundsException ex) {
    System.out.println(ex.getMessage()); //Index 5 out of bounds for length 5
}