java - 读取最后一个控制台输出并将其保存到变量/字符串中

Question

我想从控制台读取最后的输出，然后将其保存到变量中。

假设我有以下代码和输出:

System.out.println("first");
System.out.println("second");
System.out.println("third");
            ...
   **...THE CODE HERE...**

first

second

third

现在我希望它从控制台读取最后/最新输出并将其保存到变量/字符串中。

有什么想法吗？

Answer 1

这个任务很奇怪，但这里有一个快速而肮脏的解决方案:

import java.io.FilterOutputStream;
import java.io.IOException;
import java.io.OutputStream;
import java.io.PrintStream;
import java.io.StringWriter;


public class FilterOutput {
    static class MemorizingOutputStream extends FilterOutputStream {
        StringWriter sw = new StringWriter();
        String last = null;

        public MemorizingOutputStream(OutputStream out) {
            super(out);
        }

        @Override
        public void write(int b) throws IOException {
            write(new byte[] {(byte)b}, 0, 1);
        }

        @Override
        public void write(byte[] b) throws IOException {
            write(b, 0, b.length);
        }

        @Override
        public void write(byte[] b, int off, int len) throws IOException {
            out.write(b, off, len);
            String s = new String(b, off, len);
            int pos = s.lastIndexOf('\n');
            if(pos == -1) {
                sw.append(s);
            } else {
                int pos2 = s.lastIndexOf('\n', pos-1);
                if(pos2 == -1) {
                    sw.append(s.substring(0, pos));
                    last = sw.toString();
                } else {
                    last = s.substring(pos2+1, pos); 
                }
                sw = new StringWriter();
                sw.append(s.substring(pos+1));
            }
        }

        public String getLast() {
            return last;
        }

    }
    public static void main(String[] args) {
        MemorizingOutputStream memOut = new MemorizingOutputStream(System.out);
        System.setOut(new PrintStream(memOut));

        System.out.println("first");
        System.out.println("second");
        System.out.println("third");

        System.err.println(memOut.getLast());
    }
}

首先，它用记住最后一个字符串的特殊流替换标准输出流(假设字符串以 '\n' 结尾)。然后您可以查询该流以获取最后打印的字符串。请注意，此实现不是线程安全的。