Java循环内goto语句的替代方案

众所周知，Java虚拟机根本没有实现goto关键字。我的一个函数需要这样的算法，在一个循环里，如果某一次循环不满足条件，那么整个循环需要重新开始。比如下面的例子，我想连续3次打印出随机数都是0的情况。

	private void incorrectGotoSample() {
		int printNum = 3;
		Random r = new Random();
		int ri = r.nextInt(2);

		LABEL: for (int i = 0; i < printNum ; i++) {
			ri = r.nextInt(2);
			System.out.println("ri = " + ri);

			if (ri > 0) {
				goto LABEL; // "goto" not realized in Java
			}
			System.out.println("you are here!");
		}
	}

考虑了半天，Java里还是能简单实现这样的想法的。替换方案如下，在外层加一个无限循环，使用break跳出不满足情况时的循环状态，并再次使用break跳出无限循环：

private void gotoSample() {
		int printNum = 3;
		Random r = new Random();
		int ri = r.nextInt(2);

		while (true) {
			int i = 0;
			for (i = 0; i < printNum ; i++) {
				ri = r.nextInt(2);
				System.out.println("ri = " + ri);

				if (ri >= 1) {
					break;
				}

				System.out.println("you are here!");
			}
			if (i == printNum) {
				break;
			}
		}
	}

程序的某次执行结果如下，显示其满足我们的需要。

ri = 1
ri = 1
ri = 1
ri = 0
you are here!
ri = 1
ri = 1
ri = 1
ri = 1
ri = 0
you are here!
ri = 0
you are here!
ri = 1
ri = 0
you are here!
ri = 0
you are here!
ri = 0
you are here!

评论

2 楼 metaphy 2012-08-14  

continue label 和break label 都没法简单的实现

1 楼 somefuture 2012-08-14  

break也可以用标签。用continue lable1。