『Java』最简教程

最简单的Java教程，全是代码。不适合零基础的同学。只为提醒记忆而用。

不定时更新……

package demo; // Must be the first row!

import demo.ClassName;

public class process extends Object {
	public static void main(String[] args) {

		System.out.println("Hello, This is Java!");
		System.out.println("-----------------------------------------------");

		// if sentence
		boolean condition = true;
		if (condition) {
			System.out.println("This is if sentence! The condition is true");
			System.out
					.println("-----------------------------------------------");
		} else if (condition) {
			System.out
					.println("This is if sentence! The condition is another true");
			System.out
					.println("-----------------------------------------------");
		} else {
			System.out.println("This is if sentence! The condition is false");
			System.out
					.println("-----------------------------------------------");
		}

		// max = (a>b)?a:b
		int a = 2;
		int b = 1;
		int max = (a > b) ? a : b;
		System.out.println("This is max=(a>b)?a:b! Now, max is " + max);
		System.out.println("-----------------------------------------------");

		// switch sentence
		char switch_condition = 'a';
		switch (switch_condition) {
		case 'a':
			System.out.println("This is switch sentence! The case is '"
					+ switch_condition + "'");
			System.out
					.println("-----------------------------------------------");
			break;
		case 'b':
			break;
		default:
			break;
		}

		// while sentence
		int while_condition = 5;
		while (while_condition > 0) {
			while_condition--;
			if (while_condition != 1) {
				System.out.println("This is the the continue sentence!");
				continue; // Go to the next cycle!
			} else {
				System.out.println("This is the break sentence!");
				break; // Jump out of the cycle!
			}

		}
		System.out.println("End of the while sentence! while_condition is "
				+ while_condition + " now.");
		System.out.println("-----------------------------------------------");

		// do ... while
		do {
			while_condition++;
		} while (while_condition < 5); // While the condition expression is
										// true, go on the cycle!
		System.out.println("This is do...while sentence! while_condition is "
				+ while_condition + " now.");
		System.out.println("-----------------------------------------------");

		// for sentence
		for (int for_condition = 0; for_condition < 5; for_condition++) {
			System.out.println("This is for sentence! for_condition is "
					+ for_condition + " now.");
		}
		System.out.println("-----------------------------------------------");
		
		try{
			throw new Error("try...catch(error)...");
		}
		catch(Error ee){
			System.out.println(ee.getMessage());
		}
		finally{
			System.out.println("Finally!");
		}
	}

	void array_about() {
		int[] array_int;
		array_int = new int[10]; // Array must be initialed!
		array_int[0] = 1;
		int array_int_2[];
		array_int_2 = new int[10];
		char[] array_char = { 'a', 'b', 'c' };

	}
}

class class_about extends process {
	demo.ClassName cn = new demo.ClassName();

	void array_about() {
		System.out.println("Overwrite the array_about method!");
		super.array_about(); // process.array_about()
	}
}

abstract class abstract_class_about {

	// Only statement in the abstract class!

	int i;

	abstract void abstract_method();

	void abstract_method_2() {
		// ...
	}
}

interface interface_about {
	final int i = 1; // Must be final! Must be initial!

	abstract void interface_abstract_method(); // Must be abstract!
}