@Builder

public class Test{
    private Integer number;
    private String str;
    
    public static class Builder{
        private Integer number;
        private String str;
        
        public Builder number(Integer number){
            this.number = number;
            return number;
        }
        
        public Builder str(String str){
            this.str = str;
            return this;
        }
        
        public Test build(){
            return new Test(number, str);
        }
    }
}

public class TestMain{
   @Test
   void test1(){
       Test test = Test.builder()
                       .number(1)
                       .str("test")
                       .build();
       System.out.println("output : " + test.getNumber() + " " + test.getStr());
       
       Test test2 = Test.builder()
                       .str("test2")
                       .number(2)
                       .build();
       System.out.println("output : " + test2.getNumber() + " " + test2.getStr());
   }
}

@Builder
@Getter
public class Test{
    private Integer number;
    private String str;
}

public class TestMain{
   @Test
   void test1(){
       Test test = Test.builder()
                       .number(1)
                       .str("test")
                       .build();
       System.out.println("output : " + test.getNumber() + " " + test.getStr());
   }
}

// 아래와 같이 변수에 값을 지정하여도 default값으로 셋팅되지 않음
private String str = "default";

// Builder 디폴트 설정
@Builder.Default
private String str=  "default";