CodeModelIfForExample.java

public class CodeModelIfForExample {
    
    private static final String CLASS_NAME = "TestClass";

    public static void main(String args[]) throws Exception{
        JCodeModel codeModel = new JCodeModel();
        
        JDefinedClass c = codeModel._class(CLASS_NAME);
        
        writeIfElse(codeModel, c);
        writeForLoop(codeModel, c);
        
        StringCodeWriter codeWriter = new StringCodeWriter();
        codeModel.build(codeWriter);
        
        System.out.println(codeWriter.getOutput().get(CLASS_NAME + ".java"));
    }
    
    public static void writeIfElse(JCodeModel codeModel, JDefinedClass c){
        JMethod method = c.method(JMod.PUBLIC, codeModel.VOID, "testIf");
        
        JVar input = method.param(codeModel.INT, "input");
        JBlock body = method.body();
        
        JConditional condition = body._if(input.lt(JExpr.lit(42)));
        condition._then().add(
                codeModel.ref(System.class).staticRef("out").invoke("println").arg(JExpr.lit("hello")));
        
        condition._else().add(
                codeModel.ref(System.class).staticRef("out").invoke("println").arg(JExpr.lit("world")));
    }
    
    public static void writeForLoop(JCodeModel codeModel, JDefinedClass c){
        JMethod method = c.method(JMod.PUBLIC, codeModel.VOID, "testFor");
        
        JVar input = method.param(int.class, "input");
        
        JBlock body = method.body();
        
        JForLoop forLoop = body._for();
        JVar ivar = forLoop.init(codeModel.INT, "i", JExpr.lit(0));
        forLoop.test(ivar.lt(JExpr.lit(42)));
        forLoop.update(ivar.assignPlus(JExpr.lit(1)));
        
        forLoop.body().add(
                codeModel.ref(System.class).staticRef("out").invoke("println").arg(ivar));
        
    }
    
    public static class StringCodeWriter extends CodeWriter {

        private Map<String, ByteArrayOutputStream> streams = new HashMap<String, ByteArrayOutputStream>();

        @Override
        public OutputStream openBinary(JPackage pkg, String fileName) throws IOException {
            String packageFileName = pkg.name() + fileName;
            if (!streams.containsKey(packageFileName)) {
                streams.put(packageFileName, new ByteArrayOutputStream());
            }

            return streams.get(packageFileName);
        }

        @Override
        public void close() throws IOException {
            for (OutputStream outputStream : streams.values()) {
                outputStream.flush();
                outputStream.close();
            }
        }

        public String getValue(String packageFileName) {
            return new String(streams.get(packageFileName).toByteArray());
        }

        public Map<String, String> getOutput() {
            Map<String, String> outputMap = new HashMap<String, String>();

            for (Map.Entry<String, ByteArrayOutputStream> byteStreamEntry : streams.entrySet()) {
                outputMap.put(byteStreamEntry.getKey(),
                        new String(byteStreamEntry.getValue().toByteArray()));
            }

            return outputMap;
        }
    }   
}