关于String.equals(null)

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public class Than {    public static void main(String[] args) {        fun(null,"abc");    }    public static void fun(String i, String j) {        //String = String        try {            if(i == j) {                System.out.println("执行");            }        }catch(Exception ex) {            System.out.println("============");            ex.printStackTrace();        }finally {            System.out.println("结束");        }        System.out.println("+++++++++++++");        //String.equals(String)        try {            if(i.equals(j)) {                System.out.println("执行");            }        }catch(Exception ex) {            System.out.println("============");            ex.printStackTrace();        }finally {            System.out.println("结束");        }        System.out.println("+++++++++++++");        //String.equals(String)        try {            if(j.equals(i)) {                System.out.println("执行");            }        }catch(Exception ex) {            System.out.println("============");            ex.printStackTrace();        }finally {            System.out.println("结束");        }    }}

结束+++++++++++++============结束+++++++++++++结束java.lang.NullPointerException    at trycatch.Than.fun(Than.java:23)    at trycatch.Than.main(Than.java:5)

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