程序代码：

import java.lang.reflect.Field;
public class VarTest {
    private int a = 2;
    private int b = 3;
    
    //获取类中所有的成员变量
    public Field[] getFields()throws Exception{
        return VarTest.class.getDeclaredFields();
    }
    //按成员变量出现的顺序输出
    public String getOutputInOrder()throws Exception{
        StringBuffer name = new StringBuffer();
        StringBuffer value = new StringBuffer();
        Field[] fields = getFields();
        for(Field field:fields){
            name.append(field.getName());
            value.append(field.get(this));
        }
        return "" + name + "=" + value;
    }
    //按成员变量出现的顺序的相反顺序输出
    public String getOutputReverseOrder()throws Exception{
        StringBuffer name = new StringBuffer();
        StringBuffer value = new StringBuffer();
        Field[] fields = getFields();
        for(int i=fields.length-1; i>=0; i--){
            name.append(fields[i].getName());
            value.append(fields[i].get(this));
        }
        return "" + name + "=" + value;
    }
    
    public static void main(String[] args) throws Exception{
        VarTest test = new VarTest();
        System.out.println(test.getOutputInOrder());
        System.out.println(test.getOutputReverseOrder());
    }
}

程序代码：

public class GetNum {
    private int a,b,c,d;
    
    private int getAB(){
        return a*10 + b;
    }
    
    private int getCD(){
        return c*10 + d;
    }
    
    private int getDC(){
        return d*10 + c;
    }
    
    public void getABCD(){
        for(a=1; a<10; a++)
            for(b=1; b<10; b++)
                for(c=1; c<10; c++)
                    for(d=1; d<10; d++){
                        if(getAB()+getCD() == getDC())
                            System.out.println(getAB() + "+" + getCD() + "=" +  getDC());
                        }
    }
    
    public static void main(String[] args) {
        new GetNum().getABCD();
    }
}

程序代码：

public class GetNum {
    private int a,b,c,d;
    
    private int getXY(int x,int y){
        return x*10 + y;
    }
    
    public void getABCD(){
        for(a=1; a<10; a++)
            for(b=1; b<10; b++)
                for(c=1; c<10; c++)
                    for(d=1; d<10; d++){
                        if(getXY(a,b)+getXY(c,d) == getXY(d,c))
                            System.out.println(getXY(a,b) + "+" + getXY(c,d) + "=" +  getXY(d,c));
                        }
    }
    
    public static void main(String[] args) {
        new GetNum().getABCD();
    }
}