如果即使評估為真，語句也不會執行

Question

在以下代碼中， if(timesout[entry] == "exit")下的塊將永遠不會執行。 我已經驗證了當前循環的timesout[entry]在調試模式下以及通過在評估if語句之前打印出變量而將其設置為“退出”，但是無論如何，當我進入exit時該塊永遠不會執行提示，我為此感到困惑。

import java.util.Scanner;

public class timetracker {
public static void main(String args[]) {
    boolean exit = false;
    String[] reasons = new String[30];
    String[] timesout = new String[30];
    String[] timesin = new String[30];
    int entry = 0;
    Scanner keyinput = new Scanner(System.in);

    recordloop:
    while(exit == false) {
        //record info



        System.out.println("Enter time out:");
        timesout[entry] = keyinput.nextLine();

        if(timesout[entry] == "exit") {
            exit = true;
            break recordloop;   
        }

        System.out.println("Enter reason:");
        reasons[entry] = keyinput.nextLine();
        System.out.println("Enter time in:");
        timesin[entry] = keyinput.nextLine();

        entry = entry + 1;

    }

    System.out.println("Times away from phone:\n ----- \n");
    int count = entry;
    entry = entry + 1;

    while(count < entry) {
        System.out.println(reasons[count] + ": " + timesout[count] + " - " + timesin[count] + "\n");
        count = count + 1;
    }
}
}

Answer 1

timesout[entry] == "exit"

使用equals()比較字符串， ==比較引用相等

看到

• Java String.equals與==
• 面試：Java等於

Answer 2

代替

if(timesout[entry] == "exit") 

采用

if(timesout[entry].equals("exit"))

要么

if("exit".equals(timesout[entry]))

==和equals（）之間的更多信息有所不同

 http://stackoverflow.com/questions/12171783/how-is-it-possible-for-two-string-objects-with-identical-values-not-to-be-equal/12171818#12171818 

Answer 3

你能試一下嗎

if("exit".equals(timesout[entry]))

代替

if(timesout[entry] == "exit")

正如@Jigar Joshi指出的那樣，您應該看到 ==和equals()的區別和含義