W3School TIY Editor

public class Main { public static void main(String[] args) { // 启用断言 ClassLoader loader = ClassLoader.getSystemClassLoader(); loader.setDefaultAssertionStatus(true); // 运行断言示例 AssertExample example = new AssertExample(); example.run(); } } class AssertExample { public void run() { int a = 12; try { assert a == 12; // 不带错误信息的断言 assert a == 12 : "a 不等于 12"; assert a == 15 : "a 不等于 15"; } catch (AssertionError e) { System.out.println(e.getMessage()); } } }