ASMSupport教程4.7 生成关系运算符

在java中，关系运算符是很常用的， 分别是>,==,<,>=,<=,!=这六种，我们按照惯例看看我们需要生成的代码：< /p>

public static void main(String[] args) {

Random rand = new Random();
int i = rand.nextInt(100);
int j = rand.nextInt(100);
System.out.println("i = " + i);
System.out.println("j = " + j);
System.out.println("i > j is " + (i > j));
System.out.println("i < j is " + (i < j));
System.out.println("i >= j is " + (i >= j));
System.out.println("i <= j is " + (i <= j));
System.out.println("i == j is " + (i == j));
System.out.println("i != j is " + (i != j));
System.out.println("(i < 10) && (j < 10) is " + ((i < 10) && (j < 10)));
System.out.println("(i < 10) || (j < 10) is " + ((i < 10) || (j < 10)));

}

这里用到了非常多的关系运算符，那么对应的amssupport代码如下：

package example.operators;

import java.util.Random;

import org.objectweb.asm.Opcodes;


import jw.asmsupport.block.method.common.StaticMethodBody;
import jw.asmsupport.clazz.AClass;
import jw.asmsupport.clazz.AClassFactory;
import jw.asmsupport.creator.ClassCreator;
import jw.asmsupport.definition.value.Value;
import jw.asmsupport.definition.variable.LocalVariable;


import example.AbstractExample;

public class RelationalOperatorGenerate extends AbstractExample {

    public static void main(String[] args) {
        ClassCreator creator = new ClassCreator(Opcodes.V1_5, Opcodes.ACC_PUBLIC , "generated.operators.RelationalOperatorGenerateExample", null, null);

        /*
         * 
         */
        creator.createStaticMethod("main", new AClass[]{AClassFactory.getProductClass(String[].class)}, new String[]{"args"}, null, null,
                Opcodes.ACC_PUBLIC + Opcodes.ACC_STATIC, new StaticMethodBody(){

            @Override
            public void generateBody(LocalVariable... argus) {
                //Random rand = new Random();
                LocalVariable rand = createVariable("rand", AClassFactory.getProductClass(Random.class), false, 
                    invokeConstructor(AClassFactory.getProductClass(Random.class)));

                //int i = rand.nextInt(100);
                LocalVariable i = createVariable("i", AClass.INT_ACLASS, false, 
                    invoke(rand, "nextInt", Value.value(100)));

                //int j = rand.nextInt(100);
                LocalVariable j = createVariable("j", AClass.INT_ACLASS, false, 
                    invoke(rand, "nextInt", Value.value(100)));

                //System.out.println("i = " + i);
                invoke(systemOut, "println", append(Value.value("i = "), i));

                //System.out.println("j = " + j);
                invoke(systemOut, "println", append(Value.value("j = "), j));

                //System.out.println("i > j is " + (i > j));
                invoke(systemOut, "println", append(Value.value("i > j is "), greaterThan(i, j)));

                //System.out.println("i < j is " + (i < j));
                invoke(systemOut, "println", append(Value.value("i < j is "), lessThan(i, j)));

                //System.out.println("i >= j is " + (i >= j));
                invoke(systemOut, "println", append(Value.value("i >= j is "), greaterEqual(i, j)));

                //System.out.println("i <= j is " + (i <= j));
                invoke(systemOut, "println", append(Value.value("i <= j is "), lessEqual(i, j)));

                //System.out.println("i == j is " + (i == j));
                invoke(systemOut, "println", append(Value.value("i == j is "), equal(i, j)));

                //System.out.println("i != j is " + (i != j));
                invoke(systemOut, "println", append(Value.value("i != j is "), notEqual(i, j)));

                //System.out.println("(i < 10) && (j < 10) is " + ((i < 10) && (j < 10)));
                invoke(systemOut, "println", append(Value.value("(i < 10) && (j < 10) is "), 
                    conditionalAnd(lessThan(i, Value.value(10)), lessThan(j, Value.value(10)))));

                //System.out.println("(i < 10) || (j < 10) is " + ((i < 10) || (j < 10)));
                invoke(systemOut, "println", append(Value.value("(i < 10) || (j < 10) is "), 
                    conditionalOr(lessThan(i, Value.value(10)), lessThan(j, Value.value(10)))));

                runReturn();
            }
        });
        generate(creator);
    }

}

这里面我们主要介绍这关系运算所对应的asmsupport的方法（这些方法都是属于jw.asmsupport.block.ProgramBlock的）：

public final GreaterThan greaterThan(Parameterized factor1, Parameterized factor2)： >运算符的操作。

public final GreaterThan greaterEqual(Parameterized factor1, Parameterized factor2) : >=运算符。

public final GreaterThan lessThan(Parameterized factor1, Parameterized factor2) : <运算符。

public final GreaterThan lessEqual(Parameterized factor1, Parameterized factor2) : <=运算符。

public final GreaterThan lessEqual(Parameterized factor1, Parameterized factor2) : ==运算符。

public final GreaterThan lessEqual(Parameterized factor1, Parameterized factor2) : !=运算符。

这些方法都有两个参数，分别表示运算符前后的两个参数。比如a==b，那么factor1表示a，factor2表示b

 

上面asmsupport代码中还有conditionalAnd和conditionalOr方法，这是逻辑运算符，将在以后讲解。