Question

下面这段JAVA代码为什么会报空指针异常?

public class DemoTest1 {
private String[] s;
public String[] getS() {
return s;
}
public void setS(String[] s) {
this.s = s;
}
public static void main(String[] args) {
DemoTest1 test1=new DemoTest1();
String[] s2 = test1.getS();
for (int i = 0; i < 3; i++) {
s2[i]="sss"+i;
System.out.println(s2[i]);
}
}
}

Answer 1

数组s的大小没有定，还是空的。可以这样改一下：

public class DemoTest1 {
    private String[] s = new String[3];    //这里改一下
    public String[] getS() {
        return s;
    }
    public void setS(String[] s) {
        this.s = s;
    }
    public static void main(String[] args) {
        DemoTest1 test1 = new DemoTest1();
        String[] s2 = test1.getS();
        for (int i = 0; i < 3; i++) {
            s2[i] = "sss" + i;
            System.out.println(s2[i]);
        }
    }
}