代码已经上传github有兴趣的同学可以上去看看，欢迎补充
https://github.com/shubiaodian/operata_code

1.利用三元运算符，在if else分支较少的情况下

原始代码：

    public static String choice(String type){
        if("Integer".equals(type)){
            return "this is Integer";
        }
        return null;
    }

优化后的代码

    public static String choice(String type){
        return "Integer".equals(type)?"this is Integer":null;
    }

2-3的原始代码

    public static String choice(String type){
        if("Integer".equals(type)){
            return "this is Integer";
        }
        if("Long".equals(type)){
            return "this is Long";
        }
        if("String".equals(type)){
            return "this is String";
        }
        else {
            return "null";
        }
    }

2.传参为byte,char,short,int 的时候，可以使用switch case

    public static String choice(String type) {
        TypeEnum typeEnum = TypeEnum.getTypeEnumFromValue(type);
        switch (typeEnum.getCode()) {
            case 1:
                return "this is Integer";
            case 2:
                return "this is Long";
            case 3:
                return "this is String";
            default:
                return "null";
        }
    }

将各种类型通过枚举方式定义

public enum TypeEnum {
    NULL(-1,"null"),
    INTEGER(1,"Integer"),
    LONG(2,"Long"),
    STRING(3,"String");
    int code;
    String value;
    TypeEnum(int code,String value){
        this.code=code;
        this.value=value;
    }

    public int getCode() {
        return code;
    }

    public void setCode(int code) {
        this.code = code;
    }

    public String getValue() {
        return value;
    }

    public void setValue(String value) {
        this.value = value;
    }

    public static HashMap<String,TypeEnum> allValues=new HashMap<String, TypeEnum>(){
        {
            TypeEnum[] values=TypeEnum.values();
            for(int i=0;i<values.length;i++){
                this.put(values[i].value,values[i]);
            }
        }
    };

    public static TypeEnum getTypeEnumFromValue(String value){
        if(allValues.containsKey(value)) {
            return allValues.get(value);
        }
        return NULL;
    }
}

3.策略模式+工厂方法重构代码

策略接口

public interface Strategy {
    public String getType();
}

三种实现

public class IntegerTypeStrategy implements Strategy {
    public String getType() {
        return "this is Integer";
    }
}

public class LongTypeStrategy implements Strategy {
    public String getType() {
        return "this is Long";
    }
}


public class StringTypeStrategy implements Strategy {

    public String getType() {
        return "this is String";
    }
}

工厂方法

public class TypeFactory {
    public static HashMap<String,Strategy> strategys=new HashMap<String, Strategy>();
    static {
        strategys.put("Integer",new IntegerTypeStrategy());
        strategys.put("Long",new IntegerTypeStrategy());
        strategys.put("String",new IntegerTypeStrategy());
    }
    public static Strategy getStrategy(String type){
        return strategys.get(type);
    }
}

优化后的方法

    public static String choice3(String type){
        return TypeFactory.getStrategy(type).getType();
    }

4.利用枚举类重构代码

package com.optimize.code.goodcase.choice.choice4;

import java.util.HashMap;

/**
 * @author rockyluo
 * @date 2020-03-22 21:09
 **/
public enum TypeEnum {
    NULL(-1,"null"){
        @Override
        public String getType() {
            return "";
        }
    },
    INTEGER(1,"Integer"){
        @Override
        public String getType() {
            return "this is Integer";
        }
    },
    LONG(2,"Long"){
        @Override
        public String getType() {
            return "this is Long";
        }
    },
    STRING(3,"String"){
        @Override
        public String getType() {
            return "this is String";
        }
    }
    ;
    int code;
    String value;
    TypeEnum(int code, String value){
        this.code=code;
        this.value=value;
    }

    public int getCode() {
        return code;
    }

    public   abstract String getType();

    public void setCode(int code) {
        this.code = code;
    }

    public String getValue() {
        return value;
    }

    public void setValue(String value) {
        this.value = value;
    }

    public static HashMap<String, TypeEnum> allValues=new HashMap<String, TypeEnum>(){
        {
            TypeEnum[] values= TypeEnum.values();
            for(int i=0;i<values.length;i++){
                this.put(values[i].value,values[i]);
            }
        }
    };

    public static TypeEnum getTypeEnumFromValue(String value){
        if(allValues.containsKey(value)) {
            return allValues.get(value);
        }
        return NULL;
    }
}

优化之后的方法

    public static String choice(String type){

        return TypeEnum.getTypeEnumFromValue(type).getType();
    }